old_contents: # Copyright 2018 Google LLC.
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions
  # are met:
  #
  # 1. Redistributions of source code must retain the above copyright notice,
  #    this list of conditions and the following disclaimer.
  #
  # 2. Redistributions in binary form must reproduce the above copyright
  #    notice, this list of conditions and the following disclaimer in the
  #    documentation and/or other materials provided with the distribution.
  #
  # 3. Neither the name of the copyright holder nor the names of its
  #    contributors may be used to endorse or promote products derived from this
  #    software without specific prior written permission.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  # ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
  # LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  # CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  # SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  # INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  # CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  # ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  # POSSIBILITY OF SUCH DAMAGE.
  """A Python interface for files."""
  
  from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  
  import six
  
  from third_party.nucleus.io.python import gfile
  
  
  def Exists(filename):
    return gfile.Exists(filename)
  
  
  def Glob(pattern):
    return gfile.Glob(pattern)
  
  
  class ReadableFile(six.Iterator):
    """Wraps gfile.ReadableFile to add iteration, enter/exit and readlines."""
  
    def __init__(self, filename):
      self._file = gfile.ReadableFile.New(filename)
  
    def __enter__(self):
      return self
  
    def __exit__(self, type_, value, traceback):
      self._file.__exit__()
  
    def __iter__(self):
      return self
  
    def __next__(self):
      ok, line = self._file.Readline()
      if ok:
        return line
      else:
        raise StopIteration
  
    def readlines(self):
      lines = []
      while True:
        ok, line = self._file.Readline()
        if ok:
          lines.append(line)
        else:
          break
      return lines
  
  
  def Open(filename, mode="r"):
    if mode == "r":
      return ReadableFile(filename)
    elif mode == "w":
      return gfile.WritableFile.New(filename)
    else:
      raise ValueError("Unsupported mode '{}' for Open".format(mode))
  
new_contents: # Copyright 2018 Google LLC.
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions
  # are met:
  #
  # 1. Redistributions of source code must retain the above copyright notice,
  #    this list of conditions and the following disclaimer.
  #
  # 2. Redistributions in binary form must reproduce the above copyright
  #    notice, this list of conditions and the following disclaimer in the
  #    documentation and/or other materials provided with the distribution.
  #
  # 3. Neither the name of the copyright holder nor the names of its
  #    contributors may be used to endorse or promote products derived from this
  #    software without specific prior written permission.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  # ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
  # LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  # CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  # SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  # INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  # CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  # ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  # POSSIBILITY OF SUCH DAMAGE.
  """A Python interface for files."""
  
  from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  
  import six
  
  from third_party.nucleus.io.python import gfile
  
  
  def Exists(filename):
    return gfile.Exists(filename)
  
  
  def Glob(pattern):
    return gfile.Glob(pattern)
  
  
  class ReadableFile(six.Iterator):
    """Wraps gfile.ReadableFile to add iteration, enter/exit and readlines."""
  
    def __init__(self, filename):
      self._file = gfile.ReadableFile.New(filename)
  
    def __enter__(self):
      return self
  
    def __exit__(self, type_, value, traceback):
      self._file.__exit__()
  
    def __iter__(self):
      return self
  
    def __next__(self):
      ok, line = self._file.Readline()
      if ok:
        return line
      else:
        raise StopIteration
  
    def readlines(self):
      lines = []
      while True:
        ok, line = self._file.Readline()
        if ok:
          lines.append(line)
        else:
          break
      return lines
  
  
  def Open(filename, mode="r"):
    if mode.startswith("r"):
      return ReadableFile(filename)
    elif mode.startswith("w"):
      return gfile.WritableFile.New(filename)
    else:
      raise ValueError("Unsupported mode '{}' for Open".format(mode))
  
subject: Allow "wb" or "rb" as GFile.Open modes.