How to use the protobuf.python.google.protobuf.json_format.ParseError function in protobuf

field = fields_by_json_name.get(name, None)
        if not field:
          field = message_descriptor.fields_by_name.get(name, None)
        if not field and _VALID_EXTENSION_NAME.match(name):
          if not message_descriptor.is_extendable:
            raise ParseError('Message type {0} does not have extensions'.format(
                message_descriptor.full_name))
          identifier = name[1:-1]  # strip [] brackets
          identifier = '.'.join(identifier.split('.')[:-1])
          # pylint: disable=protected-access
          field = message.Extensions._FindExtensionByName(identifier)
          # pylint: enable=protected-access
        if not field:
          if self.ignore_unknown_fields:
            continue
          raise ParseError(
              ('Message type "{0}" has no field named "{1}".\n'
               ' Available Fields(except extensions): {2}').format(
                   message_descriptor.full_name, name,
                   message_descriptor.fields))
        if name in names:
          raise ParseError('Message type "{0}" should not have multiple '
                           '"{1}" fields.'.format(
                               message.DESCRIPTOR.full_name, name))
        names.append(name)
        # Check no other oneof field is parsed.
        if field.containing_oneof is not None:
          oneof_name = field.containing_oneof.name
          if oneof_name in names:
            raise ParseError('Message type "{0}" should not have multiple '
                             '"{1}" oneof fields.'.format(
                                 message.DESCRIPTOR.full_name, oneof_name))

return base64.b64decode(value)
    else:
      # Checking for unpaired surrogates appears to be unreliable,
      # depending on the specific Python version, so we check manually.
      if _UNPAIRED_SURROGATE_PATTERN.search(value):
        raise ParseError('Unpaired surrogate')
      return value
  elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_ENUM:
    # Convert an enum value.
    enum_value = field.enum_type.values_by_name.get(value, None)
    if enum_value is None:
      try:
        number = int(value)
        enum_value = field.enum_type.values_by_number.get(number, None)
      except ValueError:
        raise ParseError('Invalid enum value {0} for enum type {1}.'.format(
            value, field.enum_type.full_name))
      if enum_value is None:
        if field.file.syntax == 'proto3':
          # Proto3 accepts unknown enums.
          return number
        raise ParseError('Invalid enum value {0} for enum type {1}.'.format(
            value, field.enum_type.full_name))
    return enum_value.number

def _ConvertListValueMessage(self, value, message):
    """Convert a JSON representation into ListValue message."""
    if not isinstance(value, list):
      raise ParseError(
          'ListValue must be in [] which is {0}.'.format(value))
    message.ClearField('values')
    for item in value:
      self._ConvertValueMessage(item, message.values.add())

def _ConvertInteger(value):
  """Convert an integer.

  Args:
    value: A scalar value to convert.

  Returns:
    The integer value.

  Raises:
    ParseError: If an integer couldn't be consumed.
  """
  if isinstance(value, float) and not value.is_integer():
    raise ParseError('Couldn\'t parse integer: {0}.'.format(value))

  if isinstance(value, six.text_type) and value.find(' ') != -1:
    raise ParseError('Couldn\'t parse integer: "{0}".'.format(value))

  return int(value)

if _IsMapEntry(field):
          message.ClearField(field.name)
          self._ConvertMapFieldValue(value, message, field)
        elif field.label == descriptor.FieldDescriptor.LABEL_REPEATED:
          message.ClearField(field.name)
          if not isinstance(value, list):
            raise ParseError('repeated field {0} must be in [] which is '
                             '{1}.'.format(name, value))
          if field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_MESSAGE:
            # Repeated message field.
            for item in value:
              sub_message = getattr(message, field.name).add()
              # None is a null_value in Value.
              if (item is None and
                  sub_message.DESCRIPTOR.full_name != 'google.protobuf.Value'):
                raise ParseError('null is not allowed to be used as an element'
                                 ' in a repeated field.')
              self.ConvertMessage(item, sub_message)
          else:
            # Repeated scalar field.
            for item in value:
              if item is None:
                raise ParseError('null is not allowed to be used as an element'
                                 ' in a repeated field.')
              getattr(message, field.name).append(
                  _ConvertScalarFieldValue(item, field))
        elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_MESSAGE:
          if field.is_extension:
            sub_message = message.Extensions[field]
          else:
            sub_message = getattr(message, field.name)
          sub_message.SetInParent()

"""Convert an floating point number."""
  if value == 'nan':
    raise ParseError('Couldn\'t parse float "nan", use "NaN" instead.')
  try:
    # Assume Python compatible syntax.
    return float(value)
  except ValueError:
    # Check alternative spellings.
    if value == _NEG_INFINITY:
      return float('-inf')
    elif value == _INFINITY:
      return float('inf')
    elif value == _NAN:
      return float('nan')
    else:
      raise ParseError('Couldn\'t parse float: {0}.'.format(value))

def _DuplicateChecker(js):
  result = {}
  for name, value in js:
    if name in result:
      raise ParseError('Failed to load JSON: duplicate key {0}.'.format(name))
    result[name] = value
  return result

ParseError: In case of convert problems.
  """
  if field.cpp_type in _INT_TYPES:
    return _ConvertInteger(value)
  elif field.cpp_type in _FLOAT_TYPES:
    return _ConvertFloat(value)
  elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_BOOL:
    return _ConvertBool(value, require_str)
  elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_STRING:
    if field.type == descriptor.FieldDescriptor.TYPE_BYTES:
      return base64.b64decode(value)
    else:
      # Checking for unpaired surrogates appears to be unreliable,
      # depending on the specific Python version, so we check manually.
      if _UNPAIRED_SURROGATE_PATTERN.search(value):
        raise ParseError('Unpaired surrogate')
      return value
  elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_ENUM:
    # Convert an enum value.
    enum_value = field.enum_type.values_by_name.get(value, None)
    if enum_value is None:
      try:
        number = int(value)
        enum_value = field.enum_type.values_by_number.get(number, None)
      except ValueError:
        raise ParseError('Invalid enum value {0} for enum type {1}.'.format(
            value, field.enum_type.full_name))
      if enum_value is None:
        if field.file.syntax == 'proto3':
          # Proto3 accepts unknown enums.
          return number
        raise ParseError('Invalid enum value {0} for enum type {1}.'.format(

getattr(message, field.name).append(
                  _ConvertScalarFieldValue(item, field))
        elif field.cpp_type == descriptor.FieldDescriptor.CPPTYPE_MESSAGE:
          if field.is_extension:
            sub_message = message.Extensions[field]
          else:
            sub_message = getattr(message, field.name)
          sub_message.SetInParent()
          self.ConvertMessage(value, sub_message)
        else:
          setattr(message, field.name, _ConvertScalarFieldValue(value, field))
      except ParseError as e:
        if field and field.containing_oneof is None:
          raise ParseError('Failed to parse {0} field: {1}'.format(name, e))
        else:
          raise ParseError(str(e))
      except ValueError as e:
        raise ParseError('Failed to parse {0} field: {1}.'.format(name, e))
      except TypeError as e:
        raise ParseError('Failed to parse {0} field: {1}.'.format(name, e))

def _ConvertValueMessage(self, value, message):
    """Convert a JSON representation into Value message."""
    if isinstance(value, dict):
      self._ConvertStructMessage(value, message.struct_value)
    elif isinstance(value, list):
      self. _ConvertListValueMessage(value, message.list_value)
    elif value is None:
      message.null_value = 0
    elif isinstance(value, bool):
      message.bool_value = value
    elif isinstance(value, six.string_types):
      message.string_value = value
    elif isinstance(value, _INT_OR_FLOAT):
      message.number_value = value
    else:
      raise ParseError('Unexpected type for Value message.')