Parse the mount command output.

def Parse(self, cmd, args, stdout, stderr, return_val, time_taken,
            knowledge_base):
    """Parse the mount command output."""
    _ = stderr, time_taken, args, knowledge_base  # Unused.
    self.CheckReturn(cmd, return_val)
    result = rdf_protodict.AttributedDict()
    for entry in self._field_parser.ParseEntries(stdout):
      line_str = " ".join(entry)
      mount_rslt = self.mount_re.match(line_str)
      if mount_rslt:
        device, mount_point, fs_type, option_str = mount_rslt.groups()
        result = rdf_client_fs.Filesystem()
        result.device = device
        result.mount_point = mount_point
        result.type = fs_type
        # Parse these options as a dict as some items may be key/values.
        # KeyValue parser uses OrderedDict as the native parser method. Use it.
        options = KeyValueParser(term=",").ParseToOrderedDict(option_str)
        # Keys without values get assigned [] by default. Because these keys are
        # actually true, if declared, change any [] values to True.
        for k, v in iteritems(options):
          options[k] = v or [True]
        result.options = rdf_protodict.AttributedDict(**options)
        yield result