ppError (InvalidArgType t) = "Invalid argument type " ++ ppTerm t
  ++ ", argument type must either be a context or an object of type *"
ppError (InvalidArgType t) = "Invalid argument type " ++ ppTerm t
  ++ ", argument type must either be a context or an object of type *"
ppError (InvalidArgType t) = "Invalid argument type " ++ ppTerm t
  ++ ", argument type must either be a context or an object of type *"