<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def delete(self):
 """Delete this document"""


        assert '_id' in self._document, "Can't delete documents without `_id`"

        # Send delete signal
        signal('delete').send(self.__class__, frames=[self])

        # Delete the document
        self.get_collection().delete_one({'_id': self._id})

        # Send deleted signal
        signal('deleted').send(self.__class__, frames=[self])