code: def _maybe_read_file(filename):
    
    try:
      with open(filename) as infile:
        return infile.read()
    except IOError as e:
      if e.errno == errno.ENOENT:
        return None
docs: Read the given file, if it exists.
  
    Args:
      filename: A path to a file.
  
    Returns:
      A string containing the file contents, or `None` if the file does
      not exist.