docstr: Test labels work without a provided cache.
docstr_tok: ["Test","labels","work","without","a","provided","cache","."]
code: def test_no_cache(self, mat, op):
      """Test labels work without a provided cache."""
      assert op.label() == "U"
  
imports: import pytest
  import numpy
  from scipy.stats import unitary_group
  from gate_data import TSWAP
  import pennylane
  from pennylane.wires import Wires
  from pennylane.operation import DecompositionUndefinedError
label_desc: Use image node_id 1 for calling the TestUnitaryLabels obj's underlying member method code with example usage: obj.test_no_cache(mat, op) without return types