code: def convert_param(self, method, param, value):
          
          rules = self._get_validation(method, param)
          if not rules or not rules.get('convert'):
              return value
          try:
              return rules['convert'](value)
          except ValueError:
              raise ValidationException(
                  "{0} value {1} does not validate.".format(param, value))
docs: Converts the parameter using the function 'convert' function of the
          validation rules. Same parameters as the `validate_param` method, so
          it might have just been added there. But lumping together the two
          functionalities would make overwriting harder.
  
          :param method: A function to get the validation information from (done
                         using :func:`_get_validation`).
          :type method: Python function
          :param param: Name of the parameter to validate the value for.
          :type param: str
          :param value: Value passed in for the given parameter.
          :type value: Any valid Python value
  
          :raises: :class:`wsgiservice.exceptions.ValidationException` if the
                  value is invalid for the given method and parameter.