docstr: Signatures of all sizes should give correct length when asked.
docstr_tok: ["Signatures","of","all","sizes","should","give","correct","length","when","asked","."]
code: def test_len_signature(self):
      """Signatures of all sizes should give correct length when asked."""
      x1 = np.array([1, 2, 3])
      x2 = np.array([10, 20, 30])
      inputs0 = ()
      inputs1 = x1  # NOT in a tuple
      inputs2 = (x1, x2)
  
      sig0 = shapes.signature(inputs0)
      sig1 = shapes.signature(inputs1)
      sig2 = shapes.signature(inputs2)
  
      # pylint: disable=g-generic-assert
      self.assertEqual(len(sig0), 0)
      self.assertEqual(len(sig1), 1)
      self.assertEqual(len(sig2), 2)
  
file_path: trax/trax/shapes_test.py
imports: from absl.testing import absltest
  import numpy
  from trax import shapes
  from trax.shapes import ShapeDtype
label_desc: Use image node_id 6 for calling the ShapesTest obj's underlying member method code with example usage: obj.test_len_signature() without return types