def offset_attribute(hash, offset=nil)
      offset_attr_accessor(hash, offset)
      hash.each { |ja, original| add_attribute(ja, property(original).type) }
    end
def offset_attribute(hash, offset=nil)
      offset_attr_accessor(hash, offset)
      hash.each { |ja, original| add_attribute(ja, property(original).type) }
    end
Makes a new synthetic {Class#offset_attr_accessor} attribute for each
 _method_ => _original_ hash entry.

 @param (see Class#offset_attr_accessor)