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.

def convert_param(self, method, param, value):
        """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.
        """
        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))