code: def test_labeller():
      """Test the labeller utility"""
      assert labeller(2) == ["q_1", "q_0"]
      assert labeller(3, "j") == ["j_2", "j_1", "j_0"]
  
file_path: sympy/sympy/physics/quantum/tests/test_circuitplot.py
imports: from sympy.physics.quantum.circuitplot import labeller, render_label, Mz, CreateOneQubitGate, CreateCGate
  from sympy.physics.quantum.gate import CNOT, H, SWAP, CGate, S, T
  from sympy.external import import_module
  from sympy.testing.pytest import skip
label_desc: Use image node_id 5 for calling a global function with example usage: test_labeller() without return types