message: Describe that the semantics of gfile are different.
  Fixes
diff: @@ -38,7 +38,14 @@ from tensorflow.python.util.tf_export import tf_export
  @tf_export('gfile.GFile', 'gfile.Open')
  class GFile(_FileIO):
  - """File I/O wrappers without thread locking."""
  + """File I/O wrappers without thread locking.
  +
  + Note, that this is somewhat like builtin Python file I/O, but
  + there are semantic differences to make it more efficient for
  + some backing filesystems. For example, a write mode file will
  + not be opened until the first write call (to minimize RPC
  + invocations in network filesystems).
  + """
  def __init__(self, name, mode='r'):
  super(GFile, self).__init__(name=name, mode=mode)
  @@ -46,7 +53,14 @@ class GFile(_FileIO):
  @tf_export('gfile.FastGFile')
  class FastGFile(_FileIO):
  - """File I/O wrappers without thread locking."""
  + """File I/O wrappers without thread locking.
  +
  + Note, that this is somewhat like builtin Python file I/O, but
  + there are semantic differences to make it more efficient for
  + some backing filesystems. For example, a write mode file will
  + not be opened until the first write call (to minimize RPC
  + invocations in network filesystems).
  + """
  def __init__(self, name, mode='r'):
  super(FastGFile, self).__init__(name=name, mode=mode)
  