code: def _HasExpectedLineLength(self, file_object):
      
      original_file_position = file_object.tell()
      line_reader = self._CreateLineReader(file_object)
      for _ in range(0, 20):
        # Attempt to read a line that is longer than any line that should be in
        # the file.
        sample_line = line_reader.readline(self._maximum_line_length + 1)
        if len(sample_line) > self._maximum_line_length:
          file_object.seek(original_file_position)
          return False
      file_object.seek(original_file_position)
      return True
docs: Determines if a file begins with lines of the expected length.
  
      As we know the maximum length of valid lines in the DSV file, the presence
      of lines longer than this indicates that the file will not be parsed
      successfully, without reading excessive data from a large file.
  
      Args:
        file_object (dfvfs.FileIO): file-like object.
  
      Returns:
        bool: True if the file has lines of the expected length.