@classmethod<EOL><INDENT>def find_by_id(cls, id):<DEDENT>
obj = cls.find_one(cls._id_spec(id))<EOL>if not obj:<EOL><INDENT>raise NotFoundException(cls.collection, id)<EOL><DEDENT>return obj<EOL>
Finds a single document by its ID. Throws a
NotFoundException if the document does not exist (the
assumption being if you've got an id you should be
pretty certain the thing exists)