CAUTION: this test only detects the presence of any attribute, which is usually not what is required. It is more common to check for the presence of a particular attribute by using a matching clause of the form:
    has_my_attribute(_{my_attr:Attr}) ?-
    	nonvar(Attr).
Success:
      meta(X{a}).
      suspend:(X>0), meta(X).
Fail:
      meta(atom).
      meta(X).