def param_filter *args, **kwds, &blk
      if blk
        ParamFilter.with_block( self, *args, **kwds, &blk )
      else
        ParamFilter.with_methods( self, *args, **kwds )
      end
    end
def param_filter *args, **kwds, &blk
      if blk
        ParamFilter.with_block( self, *args, **kwds, &blk )
      else
        ParamFilter.with_methods( self, *args, **kwds )
      end
    end
def concern_scope &blk
   _scopes << Module.new(&blk) # Just to know the methods defined
   module_eval &blk
 ensure
   _scopes.pop
 end