old_contents: """
  ****
  YAML
  ****
  
  Read and write NetworkX graphs in YAML format.
  
  "YAML is a data serialization format designed for human readability 
  and interaction with scripting languages."
  See http://www.yaml.org for documentation.
  
  """
  __author__ = """Aric Hagberg (hagberg@lanl.gov)"""
  #    Copyright (C) 2004-2010 by 
  #    Aric Hagberg <hagberg@lanl.gov>
  #    Dan Schult <dschult@colgate.edu>
  #    Pieter Swart <swart@lanl.gov>
  #    All rights reserved.
  #    BSD license.
  
  __all__ = ['read_yaml', 'write_yaml']
  
  
  import networkx
  from networkx.utils import _get_fh
  
  def write_yaml(G, path, 
                 default_flow_style=False,  
                 encoding='UTF-8',
                 **kwds):
      """Write graph G in YAML text format to path. 
  
      See http://www.yaml.org
  
      """
      try:
          import yaml
      except ImportError:
          raise ImportError(
            "write_yaml() requires PyYAML: http://pyyaml.org/ ")
      fh=_get_fh(path,mode='w')        
      yaml.dump(G,fh,default_flow_style=default_flow_style,**kwds)
      fh.close()
      
  
  def read_yaml(path):
      """Read graph from YAML format from path.
  
      See http://www.yaml.org
  
      """
      try:
          import yaml
      except ImportError:
          raise ImportError(
            "read_yaml() requires PyYAML: http://pyyaml.org/ ")
  
      fh=_get_fh(path,mode='r')        
      G=yaml.load(fh)
      fh.close()
      return G
  
  
  # fixture for nose tests
  def setup_module(module):
      from nose import SkipTest
      try:
          import yaml
      except:
          raise SkipTest("yaml not available")
  
new_contents: """
  ****
  YAML
  ****
  Read and write NetworkX graphs in YAML format.
  
  "YAML is a data serialization format designed for human readability 
  and interaction with scripting languages."
  See http://www.yaml.org for documentation.
  
  """
  __author__ = """Aric Hagberg (hagberg@lanl.gov)"""
  #    Copyright (C) 2004-2010 by 
  #    Aric Hagberg <hagberg@lanl.gov>
  #    Dan Schult <dschult@colgate.edu>
  #    Pieter Swart <swart@lanl.gov>
  #    All rights reserved.
  #    BSD license.
  
  __all__ = ['read_yaml', 'write_yaml']
  
  import networkx as nx
  from networkx.utils import _get_fh
  
  def write_yaml(G, path, encoding='UTF-8', **kwds):
      """Write graph G in YAML format to path. 
  
      YAML is a data serialization format designed for human readability 
      and interaction with scripting languages [1]_.
  
      Parameters
      ----------
      G : graph
         A NetworkX graph
      path : file or string
         File or filename to write. 
         Filenames ending in .gz or .bz2 will be compressed.
      encoding: string, optional
         Specify which encoding to use when writing file.
  
      Examples
      --------
      >>> G=nx.path_graph(4)
      >>> nx.write_yaml(G,'test.yaml')
  
      References
      ----------
      .. [1] http://www.yaml.org
      """
      try:
          import yaml
      except ImportError:
          raise ImportError("write_yaml() requires PyYAML: http://pyyaml.org/")
      fh=_get_fh(path,mode='w')        
      yaml.dump(G,fh,**kwds)
      fh.close()
      
  
  def read_yaml(path):
      """Read graph in YAML format from path.
  
      YAML is a data serialization format designed for human readability 
      and interaction with scripting languages [1]_.
  
      Parameters
      ----------
      path : file or string
         File or filename to read.  Filenames ending in .gz or .bz2 
         will be uncompressed.
  
      Returns
      -------
      G : NetworkX graph
  
      Examples
      --------
      >>> G=nx.read_yaml('test.yaml')
   
      References
      ----------
      .. [1] http://www.yaml.org
  
      """
      try:
          import yaml
      except ImportError:
          raise ImportError("read_yaml() requires PyYAML: http://pyyaml.org/")
  
      fh=_get_fh(path,mode='r')        
      G=yaml.load(fh)
      fh.close()
      return G
  
  
  # fixture for nose tests
  def setup_module(module):
      from nose import SkipTest
      try:
          import yaml
      except:
          raise SkipTest("PyYAML not available")
  
subject: Add some documentation for YAML format.