The 'belongs_to' declaration in abstract class is actually evaluated
before the abstract class is inherited.
And the sub class which is inherited from abstract class only got all
the instance methods which were generated by the 'belongs_to'
declaration in its parent.
So, in my example,
I can never get 'Jp' or 'Cn' strings in the abstract class Property's
'belongs_to' declaration because the instance object 'temp' never saw
that declaration.