code: def test_invalid_lookup(self, sig):
      def default(x, y):
          return x + y
  
      sigs = (("ii->i", default),)
      gu_func = _GUFunc(default, "(i),(i)->(i)", signatures=sigs)
      _GUFunc(default, "(i),(i)->(i)", signatures=sigs)
  
      x = cupy.array([10], dtype="d")
      y = x
      with pytest.raises(TypeError):
          gu_func(x, y, casting="unsafe", signature=sig)
  
imports: import numpy
  import pytest
  import cupy
  from cupy import testing
  from cupy._core._gufuncs import _GUFunc
label_desc: Use image node_id 4 for calling the TestGUFuncSignatures obj's underlying member method code with example usage: obj.test_invalid_lookup(sig) and returns: unknown