# File lib/attributed_class.rb, line 164
    def initialize ( anObject, anAttr, val=nil )
      if val.nil?
        super "Missing the `#{anAttr.name}' attribute for `#{anObject}'"
      else
        super "Attribute `#{anAttr.name}' wait for a " +
              "`#{anAttr.klass.join(' or ')}' not `#{val}' in #{anObject}"
      end
    end