text: """External interface to the BeautifulSoup HTML parser.
  """
  
  __all__ = ["fromstring", "parse", "convert_tree"]
  
  import re
  from lxml import etree, html
  
  try:
      from bs4 import (
          BeautifulSoup, Tag, Comment, ProcessingInstruction, NavigableString,
          Declaration, CData, Doctype)
      _DECLARATION_OR_DOCTYPE = (Declaration, Doctype)
  except ImportError:
      from BeautifulSoup import (
          BeautifulSoup, Tag, Comment, ProcessingInstruction, NavigableString,
          Declaration, CData)
      _DECLARATION_OR_DOCTYPE = Declaration
  
  
  def fromstring(data, beautifulsoup=None, makeelement=None, **bsargs):
      """Parse a string of HTML data into an Element tree using the
      BeautifulSoup parser.
  
      Returns the root ``<html>`` Element of the tree.
  
      You can pass a different BeautifulSoup parser through the
      `beautifulsoup` keyword, and a diffent Element factory function
      through the `makeelement` keyword.  By default, the standard
      ``BeautifulSoup`` class and the default factory of `lxml.html` are
      used.
      """
      return _parse(data, beautifulsoup, makeelement, **bsargs)
  
  
  def parse(file, beautifulsoup=None, makeelement=None, **bsargs):
      """Parse a file into an ElemenTree using the BeautifulSoup parser.
  
      You can pass a different BeautifulSoup parser through the
      `beautifulsoup` keyword, and a diffent Element factory function
      through the `makeelement` keyword.  By default, the standard
      ``BeautifulSoup`` class and the default factory of `lxml.html` are
      used.
      """
      if not hasattr(file, 'read'):
          file = open(file)
      root = _parse(file, beautifulsoup, makeelement, **bsargs)
      return etree.ElementTree(root)
  
  
  def convert_tree(beautiful_soup_tree, makeelement=None):
      """Convert a BeautifulSoup tree to a list of Element trees.
  
      Returns a list instead of a single root Element to support
      HTML-like soup with more than one root element.
  
      You can pass a different Element factory through the `makeelement`
      keyword.
      """
      root = _convert_tree(beautiful_soup_tree, makeelement)
      children = root.getchildren()
      for child in children:
          root.remove(child)
      return children
  
  
  # helpers
  
  def _parse(source, beautifulsoup, makeelement, **bsargs):
      if beautifulsoup is None:
          beautifulsoup = BeautifulSoup
      if hasattr(beautifulsoup, "HTML_ENTITIES"):  # bs3
          if 'convertEntities' not in bsargs:
              bsargs['convertEntities'] = 'html'
      if hasattr(beautifulsoup, "DEFAULT_BUILDER_FEATURES"):  # bs4
          if 'features' not in bsargs:
              bsargs['features'] = ['html.parser']  # use Python html parser
      tree = beautifulsoup(source, **bsargs)
      root = _convert_tree(tree, makeelement)
      # from ET: wrap the document in a html root element, if necessary
      if len(root) == 1 and root[0].tag == "html":
          return root[0]
      root.tag = "html"
      return root
  
  
  _parse_doctype_declaration = re.compile(
      r'(?:\s|[<!])*DOCTYPE\s*HTML'
      r'(?:\s+PUBLIC)?(?:\s+(\'[^\']*\'|"[^"]*"))?'
      r'(?:\s+(\'[^\']*\'|"[^"]*"))?',
      re.IGNORECASE).match
  
  
  class _PseudoTag:
      # Minimal imitation of BeautifulSoup.Tag
      def __init__(self, contents):
          self.name = 'html'
          self.attrs = []
          self.contents = contents
  
      def __iter__(self):
          return self.contents.__iter__()
  
  
  def _convert_tree(beautiful_soup_tree, makeelement):
      if makeelement is None:
          makeelement = html.html_parser.makeelement
  
      # Split the tree into three parts:
      # i) everything before the root element: document type
      # declaration, comments, processing instructions, whitespace
      # ii) the root(s),
      # iii) everything after the root: comments, processing
      # instructions, whitespace
      first_element_idx = last_element_idx = None
      html_root = declaration = None
      for i, e in enumerate(beautiful_soup_tree):
          if isinstance(e, Tag):
              if first_element_idx is None:
                  first_element_idx = i
              last_element_idx = i
              if html_root is None and e.name and e.name.lower() == 'html':
                  html_root = e
          elif declaration is None and isinstance(e, _DECLARATION_OR_DOCTYPE):
              declaration = e
  
      # For a nice, well-formatted document, the variable roots below is
      # a list consisting of a single <html> element. However, the document
      # may be a soup like '<meta><head><title>Hello</head><body>Hi
      # all<\p>'. In this example roots is a list containing meta, head
      # and body elements.
      pre_root = beautiful_soup_tree.contents[:first_element_idx]
      roots = beautiful_soup_tree.contents[first_element_idx:last_element_idx+1]
      post_root = beautiful_soup_tree.contents[last_element_idx+1:]
  
      # Reorganize so that there is one <html> root...
      if html_root is not None:
          # ... use existing one if possible, ...
          i = roots.index(html_root)
          html_root.contents = roots[:i] + html_root.contents + roots[i+1:]
      else:
          # ... otherwise create a new one.
          html_root = _PseudoTag(roots)
  
      convert_node = _init_node_converters(makeelement)
  
      # Process pre_root
      res_root = convert_node(html_root)
      prev = res_root
      for e in reversed(pre_root):
          converted = convert_node(e)
          if converted is not None:
              prev.addprevious(converted)
              prev = converted
  
      # ditto for post_root
      prev = res_root
      for e in post_root:
          converted = convert_node(e)
          if converted is not None:
              prev.addnext(converted)
              prev = converted
  
      if declaration is not None:
          try:
              # bs4 provides full Doctype string
              doctype_string = declaration.output_ready()
          except AttributeError:
              doctype_string = declaration.string
  
          match = _parse_doctype_declaration(doctype_string)
          if not match:
              # Something is wrong if we end up in here. Since soupparser should
              # tolerate errors, do not raise Exception, just let it pass.
              pass
          else:
              external_id, sys_uri = match.groups()
              docinfo = res_root.getroottree().docinfo
              # strip quotes and update DOCTYPE values (any of None, '', '...')
              docinfo.public_id = external_id and external_id[1:-1]
              docinfo.system_url = sys_uri and sys_uri[1:-1]
  
      return res_root
  
  
  def _init_node_converters(makeelement):
      converters = {}
      ordered_node_types = []
  
      def converter(*types):
          def add(handler):
              for t in types:
                  converters[t] = handler
                  ordered_node_types.append(t)
              return handler
          return add
  
      def find_best_converter(node):
          for t in ordered_node_types:
              if isinstance(node, t):
                  return converters[t]
          return None
  
      def convert_node(bs_node, parent=None):
          # duplicated in convert_tag() below
          try:
              handler = converters[type(bs_node)]
          except KeyError:
              handler = converters[type(bs_node)] = find_best_converter(bs_node)
          if handler is None:
              return None
          return handler(bs_node, parent)
  
      def map_attrs(bs_attrs):
          if isinstance(bs_attrs, dict):  # bs4
              attribs = {}
              for k, v in bs_attrs.items():
                  if isinstance(v, list):
                      v = " ".join(v)
                  attribs[k] = unescape(v)
          else:
              attribs = dict((k, unescape(v)) for k, v in bs_attrs)
          return attribs
  
      def append_text(parent, text):
          if len(parent) == 0:
              parent.text = (parent.text or '') + text
          else:
              parent[-1].tail = (parent[-1].tail or '') + text
  
      # converters are tried in order of their definition
  
      @converter(Tag, _PseudoTag)
      def convert_tag(bs_node, parent):
          attrs = bs_node.attrs
          if parent is not None:
              attribs = map_attrs(attrs) if attrs else None
              res = etree.SubElement(parent, bs_node.name, attrib=attribs)
          else:
              attribs = map_attrs(attrs) if attrs else {}
              res = makeelement(bs_node.name, attrib=attribs)
  
          for child in bs_node:
              # avoid double recursion by inlining convert_node(), see above
              try:
                  handler = converters[type(child)]
              except KeyError:
                  pass
              else:
                  if handler is not None:
                      handler(child, res)
                  continue
              convert_node(child, res)
          return res
  
      @converter(Comment)
      def convert_comment(bs_node, parent):
          res = etree.Comment(bs_node)
          if parent is not None:
              parent.append(res)
          return res
  
      @converter(ProcessingInstruction)
      def convert_pi(bs_node, parent):
          if bs_node.endswith('?'):
              # The PI is of XML style (<?as df?>) but BeautifulSoup
              # interpreted it as being SGML style (<?as df>). Fix.
              bs_node = bs_node[:-1]
          res = etree.ProcessingInstruction(*bs_node.split(' ', 1))
          if parent is not None:
              parent.append(res)
          return res
  
      @converter(NavigableString)
      def convert_text(bs_node, parent):
          if parent is not None:
              append_text(parent, unescape(bs_node))
          return None
  
      return convert_node
  
  
  # copied from ET's ElementSoup
  
  try:
      from html.entities import name2codepoint  # Python 3
  except ImportError:
      from htmlentitydefs import name2codepoint
  
  
  handle_entities = re.compile("&(\w+);").sub
  
  
  def unescape(string):
      if not string:
          return ''
      # work around oddities in BeautifulSoup's entity handling
      def unescape_entity(m):
          try:
              return unichr(name2codepoint[m.group(1)])
          except KeyError:
              return m.group(0)  # use as is
      return handle_entities(unescape_entity, string)
  