docs: def commit(self,transaction = None):
          """Commit all pending transactions to the database.
  
          .. admonition:: Warning
  
              This operation can be **expensive** in runtime if a large number of
              documents (>100.000) is contained in the database, since it will
              cause all database indexes to be written to disk.
  
          """
          for collection in self.collections:
              store = self.get_collection_store(collection)
              store.commit()
              indexes = self.get_collection_indexes(collection)
              for index in indexes.values():
                  index.commit()
          self.in_transaction = False
          self.begin()