def increment!(field, options)
      options = options.dup
      model_name = (options.delete(:model_name) || self.class.model_name).to_s
      options[:scope] = evaluate_scope(options[:scope]) if options[:scope]
      options[:step] = evaluate_step(options[:step]) if options[:step]
      write_attribute(
          field.to_sym,
          Mongoid::Autoinc::Incrementor.new(model_name, field, options).inc
      )
    end
def increment!(field, options)
      options = options.dup
      model_name = (options.delete(:model_name) || self.class.model_name).to_s
      options[:scope] = evaluate_scope(options[:scope]) if options[:scope]
      options[:step] = evaluate_step(options[:step]) if options[:step]
      write_attribute(
          field.to_sym,
          Mongoid::Autoinc::Incrementor.new(model_name, field, options).inc
      )
    end
Set autoincrement value for the passed autoincrement field,
 using the passed options

 @param [ Symbol ] field Field to set the autoincrement value for.
 @param [ Hash ] options Options to pass through to the serializer.

 @return [ true ] The value of `write_attribute`