def update_selector(attributes, operator)
      attributes.each { |key, value| @selector[key] = { operator => value } }; self
    end
def update_selector(attributes, operator)
      attributes.each { |key, value| @selector[key] = { operator => value } }; self
    end
Update the selector setting the operator on the value for each key in the
 supplied attributes +Hash+.

 Example:

 <tt>criteria.update_selector({ :field => "value" }, "$in")</tt>