Why does a method defined using attr_accessor/_reader/_writer is not 
found by .method_defined? For example:

  $ irb
  irb(main):001:0> require 'pp'
  => true
  irb(main):002:0> PP.method_defined? :pp
  => true
  irb(main):003:0> PP.method_defined? :sharing_detection
  => false
  irb(main):004:0> PP.respond_to? :sharing_detection
  => true

-- 
dave