code: def parse_field(self, field, field_value):
          
          if type(field_value) is dict:
              # TODO: check operators and emit error
              operator = list(field_value)[0]
              if self.verify_operator(operator) is False:
                  return "Error: operator does not exist", operator
              value = field_value[operator]
          elif type(field_value) is unicode:
              operator = u'equals'
              value = field_value
          return field, operator, value
docs: Parse the operators and traduce: ES to SQLAlchemy operators