def run(self, value, model=None, context=None):
res = self.validate(value, model, context)<EOL>if not isinstance(res, Error):<EOL><INDENT>err = '<STR_LIT>'<EOL>raise InvalidErrorType(err.format(<EOL>self.__class__.__name__,<EOL>Error,<EOL>type(res))<EOL>)<EOL><DEDENT>return res<EOL>
Run validation
Wraps concrete implementation to ensure custom validators return
proper type of result.

:param value:               a value to validate
:param model:               parent model of the property
:param context:             parent model or custom context
:return:                    shiftschema.result.Error