def look_up(self, _from, _localField, _foreignField, _as):
query = {<EOL>'<STR_LIT>': _from,<EOL>'<STR_LIT>': _localField,<EOL>'<STR_LIT>': _foreignField,<EOL>'<STR_LIT>': _as<EOL>}<EOL>self._q.append({'<STR_LIT>': query})<EOL>return self<EOL>
Adds look up stage at query (left outer join)
:param _from: Specifies the collection in the same database to perform the join with.
:param _localField: Specifies the field from the documents input to the $lookup stage.
:param _foreignField: Specifies the field from the documents in the from collection.
:param _as: Specifies the name of the new array field to add to the input documents.
:return: The current object