docstr: Test that _pauli_mult raises a deprecation warning.
docstr_tok: ["Test","that","_pauli_mult","raises","a","deprecation","warning","."]
code: def test_deprecated_pauli_mult(self, p1, p2, p_ref):
      r"""Test that _pauli_mult raises a deprecation warning."""
      # pylint: disable=protected-access
      with pytest.warns(
          qml.PennyLaneDeprecationWarning,
          match="_pauli_mult is deprecated",
      ):
          result = qml.pauli.utils._pauli_mult(p1, p2)
  
      assert result == p_ref
  
imports: import numpy
  import pytest
  import pennylane
  from pennylane import RX, RY, U3, Hadamard, Hamiltonian, Hermitian, Identity, PauliX, PauliY, PauliZ, is_commuting
  from pennylane.operation import Tensor
  from pennylane.pauli import are_identical_pauli_words, are_pauli_words_qwc, binary_to_pauli, diagonalize_pauli_word, diagonalize_qwc_pauli_words, is_pauli_word, is_qwc, observables_to_binary_matrix, partition_pauli_group, pauli_group, pauli_mult, pauli_mult_with_phase, pauli_to_binary, pauli_word_to_matrix, pauli_word_to_string, qwc_complement_adj_matrix, qwc_rotation, simplify, string_to_pauli_word
label_desc: Use image node_id 1 for calling the TestObservableHF obj's underlying member method code with example usage: obj.test_deprecated_pauli_mult(p1, p2, p_ref) without return types