code: def _parse_index_value(self, kwargs):
          
          if len(kwargs) == 0:
              return None, None
          elif len(kwargs) > 1:
              raise ValueError("You can't pass more than one value expression, "
                               "you passed {}".format(",".join(kwargs.keys())))
  
          name, value = list(kwargs.items())[0]
  
          if not name.startswith('value'):
              raise ValueError("The keyword arg {} is not valid for this "
                               "function".format(name))
  
          if name == 'value':
              return ('=', value)
  
          if not name.startswith('value__'):
              raise ValueError("The keyword arg {} is not valid for this "
                               "function".format(name))
  
          operator = name[name.find('__') + 2:]
          try:
              return (self._operator_values[operator], value)
          except KeyError:
              raise ValueError(
                  "The operator {op} is not valid for index value matching. "
                  "Valid operators are {valid}"
                  .format(
                      op=operator,
                      valid=",".join(self._operator_values.keys()),
                  ),
              )
docs: Parse the HANDLER-supported subset of django's __ expression syntax