<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _current_size(self):
 """ Returns the current count of all documents, including the changes from the current changeMap. """

        deletes, adds, _ = Watch._extract_changes(self.doc_map, self.change_map, None)
        return len(self.doc_map) + len(adds) - len(deletes)