def validate(self, value, model=None, context=None):
invalid = [item for item in value if item not in self.choices]<EOL>if len(invalid):<EOL><INDENT>return Error(<EOL>self.invalid_multichoice,<EOL>dict(items='<STR_LIT:U+002CU+0020>'.join(invalid))<EOL>)<EOL><DEDENT>return Error()<EOL>
Validate
Perform value validation against validation settings and return
error object.

:param value:           list, value to check
:param model:           parent model being validated
:param context:         object or None, validation context
:return:                shiftschema.result.Error