def each_registered_block(type, &block)
        klass = self.class
        while klass.respond_to?(type)
          klass.public_send(type).each(&block)
          klass = klass.superclass
        end
      end
def each_registered_block(type, &block)
        klass = self.class
        while klass.respond_to?(type)
          klass.public_send(type).each(&block)
          klass = klass.superclass
        end
      end
run `&block` in every registered block in `#register_block_for`