--- is_a?(mod)
--- kind_of?(mod)

    self 饹 mod ȤΥ֥饹
    ⥸塼 mod 򥤥󥯥롼ɤ饹ȤΥ֥饹
    Τ줫Υ󥹥󥹤ǤȤ֤ޤ

        module M
        end
        class C < Object
          include M
        end
        class S < C
        end

        obj = S.new
        p obj.is_a? S       # true
        p obj.is_a? M       # true
        p obj.is_a? C       # true
        p obj.is_a? Object  # true
        p obj.is_a? Hash    # false

