class_docstr: Tests that the spectrum is returned as expected.
docstr: Test that an error is thrown if gates marked as encoding gates
  are not single-parameter gates.
docstr_tok: ["Test","that","an","error","is","thrown","if","gates","marked","as","encoding","gates","are","not","single-parameter","gates","."]
code: def test_input_gates_not_of_correct_form(self):
      """Test that an error is thrown if gates marked as encoding gates
      are not single-parameter gates."""
  
      dev = qml.device("default.qubit", wires=3)
  
      @qml.qnode(dev)
      def _circuit():
          qml.RX(0.1, wires=0, id="x")
          qml.Rot(0.2, 0.3, 0.4, wires=1, id="x")
          return qml.expval(qml.PauliZ(wires=0))
  
      with pytest.raises(
          ValueError, match="Can only consider one-parameter gates"
      ):
          circuit_spectrum(_circuit)()
  
file_path: pennylane/tests/fourier/test_circuit_spectrum.py
imports: import pytest
  import numpy
  import pennylane
  from pennylane import numpy
  from pennylane.fourier.circuit_spectrum import circuit_spectrum
label_desc: Use image node_id 4 for calling the TestCircuits obj's underlying member method code with example usage: obj.test_input_gates_not_of_correct_form() and returns: qml