text: """
  HTML tag classes.
  """
  __license__ = """
  This file is part of Dominate.
  
  Dominate is free software: you can redistribute it and/or modify
  it under the terms of the GNU Lesser General Public License as
  published by the Free Software Foundation, either version 3 of
  the License, or (at your option) any later version.
  
  Dominate is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU Lesser General Public License for more details.
  
  You should have received a copy of the GNU Lesser General
  Public License along with Dominate.  If not, see
  <http://www.gnu.org/licenses/>.
  """
  from .dom_tag import dom_tag, attr
  from .dom1core import dom1core
  
  try:
      basestring = basestring
  except NameError:  # py3
      basestring = str
      unicode = str
  
  underscored_classes = set(["del", "input", "map", "object"])
  
  # Tag attributes
  _ATTR_GLOBAL = set(
      [
          "accesskey",
          "class",
          "class",
          "contenteditable",
          "contextmenu",
          "dir",
          "draggable",
          "id",
          "item",
          "hidden",
          "lang",
          "itemprop",
          "spellcheck",
          "style",
          "subject",
          "tabindex",
          "title",
      ]
  )
  _ATTR_EVENTS = set(
      [
          "onabort",
          "onblur",
          "oncanplay",
          "oncanplaythrough",
          "onchange",
          "onclick",
          "oncontextmenu",
          "ondblclick",
          "ondrag",
          "ondragend",
          "ondragenter",
          "ondragleave",
          "ondragover",
          "ondragstart",
          "ondrop",
          "ondurationchange",
          "onemptied",
          "onended",
          "onerror",
          "onfocus",
          "onformchange",
          "onforminput",
          "oninput",
          "oninvalid",
          "onkeydown",
          "onkeypress",
          "onkeyup",
          "onload",
          "onloadeddata",
          "onloadedmetadata",
          "onloadstart",
          "onmousedown",
          "onmousemove",
          "onmouseout",
          "onmouseover",
          "onmouseup",
          "onmousewheel",
          "onpause",
          "onplay",
          "onplaying",
          "onprogress",
          "onratechange",
          "onreadystatechange",
          "onscroll",
          "onseeked",
          "onseeking",
          "onselect",
          "onshow",
          "onstalled",
          "onsubmit",
          "onsuspend",
          "ontimeupdate",
          "onvolumechange",
          "onwaiting",
      ]
  )
  
  
  ERR_ATTRIBUTE = "attributes"
  ERR_CONTEXT = "context"
  ERR_CONTENT = "content"
  
  
  class html_tag(dom_tag, dom1core):
      def __init__(self, *args, **kwargs):
          """
      Creates a new html tag instance.
      """
          super(html_tag, self).__init__(*args, **kwargs)
  
      # def validate(self):
      #   '''
      #   Validate the tag. This will check the attributes, context, and contents and
      #   emit tuples in the form of: element, message.
      #   '''
      #   errors = []
  
      #   errors.extend(self.validate_attributes())
      #   errors.extend(self.validate_context())
      #   errors.extend(self.validate_content())
  
      #   return errors
  
      # def validate_attributes(self):
      #   '''
      #   Validate the tag attributes.
      #   '''
      #   return []
  
      # def validate_context(self):
      #   '''
      #   Validate the tag context.
      #   '''
      #   return []
  
      # def validate_content(self):
      #   '''
      #   Validate the content of the tag.
      #   '''
      #   return []
  
      # def _check_attributes(self, *attrs):
      #   valid = set([])
      #   for attr in attrs:
      #     if hasattr(attr, '__iter__'):
      #       valid |= set(attr)
      #     else:
      #       valid.add(attr)
      #   return set(list(self.attributes.iterkeys())) - valid
  
  
  ################################################################################
  ############################### Html Tag Classes ###############################
  ################################################################################
  
  # Root element
  
  
  class html(html_tag):
      """
    The html element represents the root of an HTML document.
    """
  
      pass
      # def validate_attributes(self):
      #   errors = []
      #   for invalid in self._check_attributes(_ATTR_GLOBAL, 'manifest'):
      #     errors.append( (self, ERR_ATTRIBUTE, 'Invalid attribute: "%s"' % invalid) )
      #   return errors
  
      # def validate_context(self):
      #   if self.parent is not None and not isinstance(self.parent, iframe):
      #     return [(self, ERR_CONTEXT, 'Must be root element or child of an <iframe>')]
      #   return []
  
      # def validate_content(self):
      #   if len(self) != 2 or not isinstance(self[0], head) or not isinstance(self[1], body):
      #     return [(self, ERR_CONTENT, 'Children must be <head> and then <body>.')]
      #   return []
  
  
  # Document metadata
  
  
  class head(html_tag):
      """
    The head element represents a collection of metadata for the document.
    """
  
      pass
  
  
  class title(html_tag):
      """
    The title element represents the document's title or name. Authors should use
    titles that identify their documents even when they are used out of context,
    for example in a user's history or bookmarks, or in search results. The
    document's title is often different from its first heading, since the first
    heading does not have to stand alone when taken out of context.
    """
  
      def _get_text(self):
          return u"".join(self.get(basestring))
  
      def _set_text(self, text):
          self.clear()
          self.add(text)
  
      text = property(_get_text, _set_text)
  
  
  class base(html_tag):
      """
    The base element allows authors to specify the document base URL for the
    purposes of resolving relative URLs, and the name of the default browsing
    context for the purposes of following hyperlinks. The element does not
    represent any content beyond this information.
    """
  
      is_single = True
  
  
  class link(html_tag):
      """
    The link element allows authors to link their document to other resources.
    """
  
      is_single = True
  
  
  class meta(html_tag):
      """
    The meta element represents various kinds of metadata that cannot be
    expressed using the title, base, link, style, and script elements.
    """
  
      is_single = True
  
  
  class style(html_tag):
      """
    The style element allows authors to embed style information in their
    documents. The style element is one of several inputs to the styling
    processing model. The element does not represent content for the user.
    """
  
      is_pretty = False
  
  
  # Scripting
  
  
  class script(html_tag):
      """
    The script element allows authors to include dynamic script and data blocks
    in their documents. The element does not represent content for the user.
    """
  
      is_pretty = False
  
  
  class noscript(html_tag):
      """
    The noscript element represents nothing if scripting is enabled, and
    represents its children if scripting is disabled. It is used to present
    different markup to user agents that support scripting and those that don't
    support scripting, by affecting how the document is parsed.
    """
  
      pass
  
  
  # Sections
  
  
  class body(html_tag):
      """
    The body element represents the main content of the document.
    """
  
      pass
  
  
  class section(html_tag):
      """
    The section element represents a generic section of a document or
    application. A section, in this context, is a thematic grouping of content,
    typically with a heading.
    """
  
      pass
  
  
  class nav(html_tag):
      """
    The nav element represents a section of a page that links to other pages or
    to parts within the page: a section with navigation links.
    """
  
      pass
  
  
  class article(html_tag):
      """
    The article element represents a self-contained composition in a document,
    page, application, or site and that is, in principle, independently
    distributable or reusable, e.g. in syndication. This could be a forum post, a
    magazine or newspaper article, a blog entry, a user-submitted comment, an
    interactive widget or gadget, or any other independent item of content.
    """
  
      pass
  
  
  class aside(html_tag):
      """
    The aside element represents a section of a page that consists of content
    that is tangentially related to the content around the aside element, and
    which could be considered separate from that content. Such sections are
    often represented as sidebars in printed typography.
    """
  
      pass
  
  
  class h1(html_tag):
      """
    Represents the highest ranking heading.
    """
  
      pass
  
  
  class h2(html_tag):
      """
    Represents the second-highest ranking heading.
    """
  
      pass
  
  
  class h3(html_tag):
      """
    Represents the third-highest ranking heading.
    """
  
      pass
  
  
  class h4(html_tag):
      """
    Represents the fourth-highest ranking heading.
    """
  
      pass
  
  
  class h5(html_tag):
      """
    Represents the fifth-highest ranking heading.
    """
  
      pass
  
  
  class h6(html_tag):
      """
    Represents the sixth-highest ranking heading.
    """
  
      pass
  
  
  class hgroup(html_tag):
      """
    The hgroup element represents the heading of a section. The element is used
    to group a set of h1-h6 elements when the heading has multiple levels, such
    as subheadings, alternative titles, or taglines.
    """
  
      pass
  
  
  class header(html_tag):
      """
    The header element represents a group of introductory or navigational aids.
    """
  
      pass
  
  
  class footer(html_tag):
      """
    The footer element represents a footer for its nearest ancestor sectioning
    content or sectioning root element. A footer typically contains information
    about its section such as who wrote it, links to related documents,
    copyright data, and the like.
    """
  
      pass
  
  
  class address(html_tag):
      """
    The address element represents the contact information for its nearest
    article or body element ancestor. If that is the body element, then the
    contact information applies to the document as a whole.
    """
  
      pass
  
  
  # Grouping content
  
  
  class p(html_tag):
      """
    The p element represents a paragraph.
    """
  
      pass
  
  
  class hr(html_tag):
      """
    The hr element represents a paragraph-level thematic break, e.g. a scene
    change in a story, or a transition to another topic within a section of a
    reference book.
    """
  
      is_single = True
  
  
  class pre(html_tag):
      """
    The pre element represents a block of preformatted text, in which structure
    is represented by typographic conventions rather than by elements.
    """
  
      is_pretty = False
  
  
  class blockquote(html_tag):
      """
    The blockquote element represents a section that is quoted from another
    source.
    """
  
      pass
  
  
  class ol(html_tag):
      """
    The ol element represents a list of items, where the items have been
    intentionally ordered, such that changing the order would change the
    meaning of the document.
    """
  
      pass
  
  
  class ul(html_tag):
      """
    The ul element represents a list of items, where the order of the items is
    not important - that is, where changing the order would not materially change
    the meaning of the document.
    """
  
      pass
  
  
  class li(html_tag):
      """
    The li element represents a list item. If its parent element is an ol, ul, or
    menu element, then the element is an item of the parent element's list, as
    defined for those elements. Otherwise, the list item has no defined
    list-related relationship to any other li element.
    """
  
      pass
  
  
  class dl(html_tag):
      """
    The dl element represents an association list consisting of zero or more
    name-value groups (a description list). Each group must consist of one or
    more names (dt elements) followed by one or more values (dd elements).
    Within a single dl element, there should not be more than one dt element for
    each name.
    """
  
      pass
  
  
  class dt(html_tag):
      """
    The dt element represents the term, or name, part of a term-description group
    in a description list (dl element).
    """
  
      pass
  
  
  class dd(html_tag):
      """
    The dd element represents the description, definition, or value, part of a
    term-description group in a description list (dl element).
    """
  
      pass
  
  
  class figure(html_tag):
      """
    The figure element represents some flow content, optionally with a caption,
    that is self-contained and is typically referenced as a single unit from the
    main flow of the document.
    """
  
      pass
  
  
  class figcaption(html_tag):
      """
    The figcaption element represents a caption or legend for the rest of the
    contents of the figcaption element's parent figure element, if any.
    """
  
      pass
  
  
  class div(html_tag):
      """
    The div element has no special meaning at all. It represents its children. It
    can be used with the class, lang, and title attributes to mark up semantics
    common to a group of consecutive elements.
    """
  
      pass
  
  
  # Text semantics
  
  
  class a(html_tag):
      """
    If the a element has an href attribute, then it represents a hyperlink (a
    hypertext anchor).
  
    If the a element has no href attribute, then the element represents a
    placeholder for where a link might otherwise have been placed, if it had been
    relevant.
    """
  
      pass
  
  
  class em(html_tag):
      """
    The em element represents stress emphasis of its contents.
    """
  
      pass
  
  
  class strong(html_tag):
      """
    The strong element represents strong importance for its contents.
    """
  
      pass
  
  
  class small(html_tag):
      """
    The small element represents side comments such as small print.
    """
  
      pass
  
  
  class s(html_tag):
      """
    The s element represents contents that are no longer accurate or no longer
    relevant.
    """
  
      pass
  
  
  class cite(html_tag):
      """
    The cite element represents the title of a work (e.g. a book, a paper, an
    essay, a poem, a score, a song, a script, a film, a TV show, a game, a
    sculpture, a painting, a theatre production, a play, an opera, a musical, an
    exhibition, a legal case report, etc). This can be a work that is being
    quoted or referenced in detail (i.e. a citation), or it can just be a work
    that is mentioned in passing.
    """
  
      pass
  
  
  class q(html_tag):
      """
    The q element represents some phrasing content quoted from another source.
    """
  
      pass
  
  
  class dfn(html_tag):
      """
    The dfn element represents the defining instance of a term. The paragraph,
    description list group, or section that is the nearest ancestor of the dfn
    element must also contain the definition(s) for the term given by the dfn
    element.
    """
  
      pass
  
  
  class abbr(html_tag):
      """
    The abbr element represents an abbreviation or acronym, optionally with its
    expansion. The title attribute may be used to provide an expansion of the
    abbreviation. The attribute, if specified, must contain an expansion of the
    abbreviation, and nothing else.
    """
  
      pass
  
  
  class time_(html_tag):
      """
    The time element represents either a time on a 24 hour clock, or a precise
    date in the proleptic Gregorian calendar, optionally with a time and a
    time-zone offset.
    """
  
      pass
  
  
  _time = time_
  
  
  class code(html_tag):
      """
    The code element represents a fragment of computer code. This could be an XML
    element name, a filename, a computer program, or any other string that a
    computer would recognize.
    """
  
      pass
  
  
  class var(html_tag):
      """
    The var element represents a variable. This could be an actual variable in a
    mathematical expression or programming context, an identifier representing a
    constant, a function parameter, or just be a term used as a placeholder in
    prose.
    """
  
      pass
  
  
  class samp(html_tag):
      """
    The samp element represents (sample) output from a program or computing
    system.
    """
  
      pass
  
  
  class kbd(html_tag):
      """
    The kbd element represents user input (typically keyboard input, although it
    may also be used to represent other input, such as voice commands).
    """
  
      pass
  
  
  class sub(html_tag):
      """
    The sub element represents a subscript.
    """
  
      pass
  
  
  class sup(html_tag):
      """
    The sup element represents a superscript.
    """
  
      pass
  
  
  class i(html_tag):
      """
    The i element represents a span of text in an alternate voice or mood, or
    otherwise offset from the normal prose in a manner indicating a different
    quality of text, such as a taxonomic designation, a technical term, an
    idiomatic phrase from another language, a thought, or a ship name in Western
    texts.
    """
  
      pass
  
  
  class b(html_tag):
      """
    The b element represents a span of text to which attention is being drawn for
    utilitarian purposes without conveying any extra importance and with no
    implication of an alternate voice or mood, such as key words in a document
    abstract, product names in a review, actionable words in interactive
    text-driven software, or an article lede.
    """
  
      pass
  
  
  class u(html_tag):
      """
    The u element represents a span of text with an unarticulated, though
    explicitly rendered, non-textual annotation, such as labeling the text as
    being a proper name in Chinese text (a Chinese proper name mark), or
    labeling the text as being misspelt.
    """
  
      pass
  
  
  class mark(html_tag):
      """
    The mark element represents a run of text in one document marked or
    highlighted for reference purposes, due to its relevance in another context.
    When used in a quotation or other block of text referred to from the prose,
    it indicates a highlight that was not originally present but which has been
    added to bring the reader's attention to a part of the text that might not
    have been considered important by the original author when the block was
    originally written, but which is now under previously unexpected scrutiny.
    When used in the main prose of a document, it indicates a part of the
    document that has been highlighted due to its likely relevance to the user's
    current activity.
    """
  
      pass
  
  
  class ruby(html_tag):
      """
    The ruby element allows one or more spans of phrasing content to be marked
    with ruby annotations. Ruby annotations are short runs of text presented
    alongside base text, primarily used in East Asian typography as a guide for
    pronunciation or to include other annotations. In Japanese, this form of
    typography is also known as furigana.
    """
  
      pass
  
  
  class rt(html_tag):
      """
    The rt element marks the ruby text component of a ruby annotation.
    """
  
      pass
  
  
  class rp(html_tag):
      """
    The rp element can be used to provide parentheses around a ruby text
    component of a ruby annotation, to be shown by user agents that don't support
    ruby annotations.
    """
  
      pass
  
  
  class bdi(html_tag):
      """
    The bdi element represents a span of text that is to be isolated from its
    surroundings for the purposes of bidirectional text formatting.
    """
  
      pass
  
  
  class bdo(html_tag):
      """
    The bdo element represents explicit text directionality formatting control
    for its children. It allows authors to override the Unicode bidirectional
    algorithm by explicitly specifying a direction override.
    """
  
      pass
  
  
  class span(html_tag):
      """
    The span element doesn't mean anything on its own, but can be useful when
    used together with the global attributes, e.g. class, lang, or dir. It
    represents its children.
    """
  
      pass
  
  
  class br(html_tag):
      """
    The br element represents a line break.
    """
  
      is_single = True
      is_inline = True
  
  
  class wbr(html_tag):
      """
    The wbr element represents a line break opportunity.
    """
  
      is_single = True
      is_inline = True
  
  
  # Edits
  
  
  class ins(html_tag):
      """
    The ins element represents an addition to the document.
    """
  
      pass
  
  
  class del_(html_tag):
      """
    The del element represents a removal from the document.
    """
  
      pass
  
  
  # Embedded content
  
  
  class img(html_tag):
      """
    An img element represents an image.
    """
  
      is_single = True
  
  
  class iframe(html_tag):
      """
    The iframe element represents a nested browsing context.
    """
  
      pass
  
  
  class embed(html_tag):
      """
    The embed element represents an integration point for an external (typically
    non-HTML) application or interactive content.
    """
  
      is_single = True
  
  
  class object_(html_tag):
      """
    The object element can represent an external resource, which, depending on
    the type of the resource, will either be treated as an image, as a nested
    browsing context, or as an external resource to be processed by a plugin.
    """
  
      pass
  
  
  _object = object_
  
  
  class param(html_tag):
      """
    The param element defines parameters for plugins invoked by object elements.
    It does not represent anything on its own.
    """
  
      is_single = True
  
  
  class video(html_tag):
      """
    A video element is used for playing videos or movies, and audio files with
    captions.
    """
  
      pass
  
  
  class audio(html_tag):
      """
    An audio element represents a sound or audio stream.
    """
  
      pass
  
  
  class source(html_tag):
      """
    The source element allows authors to specify multiple alternative media
    resources for media elements. It does not represent anything on its own.
    """
  
      is_single = True
  
  
  class track(html_tag):
      """
    The track element allows authors to specify explicit external timed text
    tracks for media elements. It does not represent anything on its own.
    """
  
      is_single = True
  
  
  class canvas(html_tag):
      """
    The canvas element provides scripts with a resolution-dependent bitmap
    canvas, which can be used for rendering graphs, game graphics, or other
    visual images on the fly.
    """
  
      pass
  
  
  class map_(html_tag):
      """
    The map element, in conjunction with any area element descendants, defines an
    image map. The element represents its children.
    """
  
      pass
  
  
  class area(html_tag):
      """
    The area element represents either a hyperlink with some text and a
    corresponding area on an image map, or a dead area on an image map.
    """
  
      is_single = True
  
  
  # Tabular data
  
  
  class table(html_tag):
      """
    The table element represents data with more than one dimension, in the form
    of a table.
    """
  
      pass
  
  
  class caption(html_tag):
      """
    The caption element represents the title of the table that is its parent, if
    it has a parent and that is a table element.
    """
  
      pass
  
  
  class colgroup(html_tag):
      """
    The colgroup element represents a group of one or more columns in the table
    that is its parent, if it has a parent and that is a table element.
    """
  
      pass
  
  
  class col(html_tag):
      """
    If a col element has a parent and that is a colgroup element that itself has
    a parent that is a table element, then the col element represents one or more
    columns in the column group represented by that colgroup.
    """
  
      is_single = True
  
  
  class tbody(html_tag):
      """
    The tbody element represents a block of rows that consist of a body of data
    for the parent table element, if the tbody element has a parent and it is a
    table.
    """
  
      pass
  
  
  class thead(html_tag):
      """
    The thead element represents the block of rows that consist of the column
    labels (headers) for the parent table element, if the thead element has a
    parent and it is a table.
    """
  
      pass
  
  
  class tfoot(html_tag):
      """
    The tfoot element represents the block of rows that consist of the column
    summaries (footers) for the parent table element, if the tfoot element has a
    parent and it is a table.
    """
  
      pass
  
  
  class tr(html_tag):
      """
    The tr element represents a row of cells in a table.
    """
  
      pass
  
  
  class td(html_tag):
      """
    The td element represents a data cell in a table.
    """
  
      pass
  
  
  class th(html_tag):
      """
    The th element represents a header cell in a table.
    """
  
      pass
  
  
  # Forms
  
  
  class form(html_tag):
      """
    The form element represents a collection of form-associated elements, some of
    which can represent editable values that can be submitted to a server for
    processing.
    """
  
      pass
  
  
  class fieldset(html_tag):
      """
    The fieldset element represents a set of form controls optionally grouped
    under a common name.
    """
  
      pass
  
  
  class legend(html_tag):
      """
    The legend element represents a caption for the rest of the contents of the
    legend element's parent fieldset element, if any.
    """
  
      pass
  
  
  class label(html_tag):
      """
    The label represents a caption in a user interface. The caption can be
    associated with a specific form control, known as the label element's labeled
    control, either using for attribute, or by putting the form control inside
    the label element itself.
    """
  
      pass
  
  
  class input_(html_tag):
      """
    The input element represents a typed data field, usually with a form control
    to allow the user to edit the data.
    """
  
      is_single = True
  
  
  input = _input = input_
  
  
  class button(html_tag):
      """
    The button element represents a button. If the element is not disabled, then
    the user agent should allow the user to activate the button.
    """
  
      pass
  
  
  class select(html_tag):
      """
    The select element represents a control for selecting amongst a set of
    options.
    """
  
      pass
  
  
  class datalist(html_tag):
      """
    The datalist element represents a set of option elements that represent
    predefined options for other controls. The contents of the element represents
    fallback content for legacy user agents, intermixed with option elements that
    represent the predefined options. In the rendering, the datalist element
    represents nothing and it, along with its children, should be hidden.
    """
  
      pass
  
  
  class optgroup(html_tag):
      """
    The optgroup element represents a group of option elements with a common
    label.
    """
  
      pass
  
  
  class option(html_tag):
      """
    The option element represents an option in a select element or as part of a
    list of suggestions in a datalist element.
    """
  
      pass
  
  
  class textarea(html_tag):
      """
    The textarea element represents a multiline plain text edit control for the
    element's raw value. The contents of the control represent the control's
    default value.
    """
  
      pass
  
  
  class keygen(html_tag):
      """
    The keygen element represents a key pair generator control. When the
    control's form is submitted, the private key is stored in the local keystore,
    and the public key is packaged and sent to the server.
    """
  
      is_single = True
  
  
  class output(html_tag):
      """
    The output element represents the result of a calculation.
    """
  
      pass
  
  
  class progress(html_tag):
      """
    The progress element represents the completion progress of a task. The
    progress is either indeterminate, indicating that progress is being made but
    that it is not clear how much more work remains to be done before the task is
    complete (e.g. because the task is waiting for a remote host to respond), or
    the progress is a number in the range zero to a maximum, giving the fraction
    of work that has so far been completed.
    """
  
      pass
  
  
  class meter(html_tag):
      """
    The meter element represents a scalar measurement within a known range, or a
    fractional value; for example disk usage, the relevance of a query result, or
    the fraction of a voting population to have selected a particular candidate.
    """
  
      pass
  
  
  # Interactive elements
  
  
  class details(html_tag):
      """
    The details element represents a disclosure widget from which the user can
    obtain additional information or controls.
    """
  
      pass
  
  
  class summary(html_tag):
      """
    The summary element represents a summary, caption, or legend for the rest of
    the contents of the summary element's parent details element, if any.
    """
  
      pass
  
  
  class command(html_tag):
      """
    The command element represents a command that the user can invoke.
    """
  
      is_single = True
  
  
  class menu(html_tag):
      """
    The menu element represents a list of commands.
    """
  
      pass
  
  
  class font(html_tag):
      """
    The font element represents the font in a html .
    """
  
      pass
  
  
  # Additional markup
  
  
  class comment(html_tag):
      """
    Normal, one-line comment:
      >>> print comment("Hello, comments!")
      <!--Hello, comments!-->
  
    For IE's "if" statement comments:
      >>> print comment(p("Upgrade your browser."), condition='lt IE6')
      <!--[if lt IE6]><p>Upgrade your browser.</p><![endif]-->
  
    Downlevel conditional comments:
      >>> print comment(p("You are using a ", em("downlevel"), " browser."),
              condition='false', downlevel='revealed')
      <![if false]><p>You are using a <em>downlevel</em> browser.</p><![endif]>
  
    For more on conditional comments see:
      http://msdn.microsoft.com/en-us/library/ms537512(VS.85).aspx
    """
  
      ATTRIBUTE_CONDITION = "condition"
  
      # Valid values are 'hidden', 'downlevel' or 'revealed'
      ATTRIBUTE_DOWNLEVEL = "downlevel"
  
      def _render(self, sb, indent_level=1, indent_str="  ", pretty=True, xhtml=False):
          has_condition = comment.ATTRIBUTE_CONDITION in self.attributes
          is_revealed = (
              comment.ATTRIBUTE_DOWNLEVEL in self.attributes
              and self.attributes[comment.ATTRIBUTE_DOWNLEVEL] == "revealed"
          )
  
          sb.append("<!")
          if not is_revealed:
              sb.append("--")
          if has_condition:
              sb.append("[if %s]>" % self.attributes[comment.ATTRIBUTE_CONDITION])
  
          pretty = self._render_children(sb, indent_level - 1, indent_str, pretty, xhtml)
  
          # if len(self.children) > 1:
          if any(isinstance(child, dom_tag) for child in self):
              sb.append("\n")
              sb.append(indent_str * (indent_level - 1))
  
          if has_condition:
              sb.append("<![endif]")
          if not is_revealed:
              sb.append("--")
          sb.append(">")
  
          return sb
  