text: from __future__ import absolute_import, division, print_function
  
  import re
  import os
  from functools import partial
  
  from graphviz import Digraph
  
  from .core import istask, get_dependencies, ishashable
  from .utils import funcname
  
  
  def task_label(task):
      """Label for a task on a dot graph.
  
      Examples
      --------
      >>> from operator import add
      >>> task_label((add, 1, 2))
      'add'
      >>> task_label((add, (add, 1, 2), 3))
      'add(...)'
      """
      func = task[0]
      if hasattr(func, 'funcs'):
          if len(func.funcs) > 1:
              return '{0}(...)'.format(funcname(func.funcs[0]))
          else:
              head = funcname(func.funcs[0])
      else:
          head = funcname(task[0])
      if any(has_sub_tasks(i) for i in task[1:]):
          return '{0}(...)'.format(head)
      else:
          return head
  
  
  def has_sub_tasks(task):
      """Returns True if the task has sub tasks"""
      if istask(task):
          return True
      elif isinstance(task, list):
          return any(has_sub_tasks(i) for i in task)
      else:
          return False
  
  
  def name(x):
      try:
          return str(hash(x))
      except TypeError:
          return str(hash(str(x)))
  
  
  _HASHPAT = re.compile('([0-9a-z]{32})')
  _UUIDPAT = re.compile('([0-9a-z]{8}-[0-9a-z]{4}-[0-9a-z]{4}-[0-9a-z]{4}-[0-9a-z]{12})')
  
  
  def label(x, cache=None):
      """
  
      >>> label('x')
      'x'
  
      >>> label(('x', 1))
      "('x', 1)"
  
      >>> from hashlib import md5
      >>> x = 'x-%s-hello' % md5(b'1234').hexdigest()
      >>> x
      'x-81dc9bdb52d04dc20036dbd8313ed055-hello'
  
      >>> label(x)
      'x-#-hello'
  
      >>> from uuid import uuid1
      >>> x = 'x-%s-hello' % uuid1()
      >>> x  # doctest: +SKIP
      'x-4c1a3d7e-0b45-11e6-8334-54ee75105593-hello'
  
      >>> label(x)
      'x-#-hello'
      """
      s = str(x)
      for pattern in (_HASHPAT, _UUIDPAT):
          m = re.search(pattern, s)
          if m is not None:
              for h in m.groups():
                  if cache is not None:
                      n = cache.get(h, len(cache))
                      label = '#{0}'.format(n)
                      # cache will be overwritten destructively
                      cache[h] = n
                  else:
                      label = '#'
                  s = s.replace(h, label)
      return s
  
  
  def to_graphviz(dsk, data_attributes=None, function_attributes=None, **kwargs):
      if data_attributes is None:
          data_attributes = {}
      if function_attributes is None:
          function_attributes = {}
  
      attributes = {'rankdir': 'BT'}
      attributes.update(kwargs)
      g = Digraph(graph_attr=attributes)
  
      seen = set()
      cache = {}
  
      for k, v in dsk.items():
          k_name = name(k)
          if k_name not in seen:
              seen.add(k_name)
              g.node(k_name, label=label(k, cache=cache), shape='box',
                     **data_attributes.get(k, {}))
  
          if istask(v):
              func_name = name((k, 'function'))
              if func_name not in seen:
                  seen.add(func_name)
                  g.node(func_name, label=task_label(v), shape='circle',
                         **function_attributes.get(k, {}))
              g.edge(func_name, k_name)
  
              for dep in get_dependencies(dsk, k):
                  dep_name = name(dep)
                  if dep_name not in seen:
                      seen.add(dep_name)
                      g.node(dep_name, label=label(dep, cache=cache), shape='box',
                             **data_attributes.get(dep, {}))
                  g.edge(dep_name, func_name)
          elif ishashable(v) and v in dsk:
              g.edge(name(v), k_name)
      return g
  
  
  IPYTHON_IMAGE_FORMATS = frozenset(['jpeg', 'png'])
  IPYTHON_NO_DISPLAY_FORMATS = frozenset(['dot', 'pdf'])
  
  
  def _get_display_cls(format):
      """
      Get the appropriate IPython display class for `format`.
  
      Returns `IPython.display.SVG` if format=='svg', otherwise
      `IPython.display.Image`.
  
      If IPython is not importable, return dummy function that swallows its
      arguments and returns None.
      """
      dummy = lambda *args, **kwargs: None
      try:
          import IPython.display as display
      except ImportError:
          # Can't return a display object if no IPython.
          return dummy
  
      if format in IPYTHON_NO_DISPLAY_FORMATS:
          # IPython can't display this format natively, so just return None.
          return dummy
      elif format in IPYTHON_IMAGE_FORMATS:
          # Partially apply `format` so that `Image` and `SVG` supply a uniform
          # interface to the caller.
          return partial(display.Image, format=format)
      elif format == 'svg':
          return display.SVG
      else:
          raise ValueError("Unknown format '%s' passed to `dot_graph`" % format)
  
  
  def dot_graph(dsk, filename='mydask', format=None, **kwargs):
      """
      Render a task graph using dot.
  
      If `filename` is not None, write a file to disk with that name in the
      format specified by `format`.  `filename` should not include an extension.
  
      Parameters
      ----------
      dsk : dict
          The graph to display.
      filename : str or None, optional
          The name (without an extension) of the file to write to disk.  If
          `filename` is None, no file will be written, and we communicate with
          dot using only pipes.  Default is 'mydask'.
      format : {'png', 'pdf', 'dot', 'svg', 'jpeg', 'jpg'}, optional
          Format in which to write output file.  Default is 'png'.
      **kwargs
          Additional keyword arguments to forward to `to_graphviz`.
  
      Returns
      -------
      result : None or IPython.display.Image or IPython.display.SVG  (See below.)
  
      Notes
      -----
      If IPython is installed, we return an IPython.display object in the
      requested format.  If IPython is not installed, we just return None.
  
      We always return None if format is 'pdf' or 'dot', because IPython can't
      display these formats natively. Passing these formats with filename=None
      will not produce any useful output.
  
      See Also
      --------
      dask.dot.to_graphviz
      """
      g = to_graphviz(dsk, **kwargs)
  
      fmts = ['.png', '.pdf', '.dot', '.svg', '.jpeg', '.jpg']
      if format is None and any(filename.lower().endswith(fmt) for fmt in fmts):
          filename, format = os.path.splitext(filename)
          format = format[1:].lower()
  
      if format is None:
          format = 'png'
  
      data = g.pipe(format=format)
      if not data:
          raise RuntimeError("Graphviz failed to properly produce an image. "
                             "This probably means your installation of graphviz "
                             "is missing png support. See: "
                             "https://github.com/ContinuumIO/anaconda-issues/"
                             "issues/485 for more information.")
  
      display_cls = _get_display_cls(format)
  
      if not filename:
          return display_cls(data=data)
  
      full_filename = '.'.join([filename, format])
      with open(full_filename, 'wb') as f:
          f.write(data)
  
      return display_cls(filename=full_filename)
  