def perfom_query(iterator, &block)
      if example
        connection.by_example(example, options).each(&iterator)
      else
        connection.all(options).each(&iterator)
      end
    end
def perfom_query(iterator, &block)
      if example
        connection.by_example(example, options).each(&iterator)
      else
        connection.all(options).each(&iterator)
      end
    end
Performs the query against the database connection.

 This can be changed by subclasses to implement other types
 of queries, such as AQL queries.

 @param [Lambda] iterator To be called on each document returned from
                 the database