code: def contains(self, cond=None, doc_ids=None, eids=None):
          
          doc_ids = _get_doc_ids(doc_ids, eids)
  
          if doc_ids is not None:
              # Documents specified by ID
              return any(self.get(doc_id=doc_id) for doc_id in doc_ids)
  
          # Document specified by condition
          return self.get(cond) is not None
docs: Check wether the database contains a document matching a condition or
          an ID.
  
          If ``eids`` is set, it checks if the db contains a document with one
          of the specified.
  
          :param cond: the condition use
          :type cond: Query
          :param doc_ids: the document IDs to look for