def respond_to_missing?(method, include_private = false)
      # Short circuit if we have invalid instance variable name,
      # otherwise we get an exception that we don't need.
      return super unless valid_instance_variable? method
      if instance_variable_defined? instance_variablize(method)
        true
      else
        super
      end
    end
def respond_to_missing?(method, include_private = false)
      # Short circuit if we have invalid instance variable name,
      # otherwise we get an exception that we don't need.
      return super unless valid_instance_variable? method
      if instance_variable_defined? instance_variablize(method)
        true
      else
        super
      end
    end
Tells users that we respond to missing methods
 if they are instance variables.