'Merges query dicts - effectively &ing them together.'

def _query_conjunction(self, queries):

    query_ops = set()
    combined_query = {}
    for query in queries:
        ops = set(query.keys())
        intersection = ops.intersection(query_ops)
        if intersection:
            raise DuplicateQueryConditionsError()
        query_ops.update(ops)
        combined_query.update(copy.deepcopy(query))
    return combined_query
