class_docstr: Tests for simple single-qutrit observables
class_docstr_tok: ["Tests","for","simple","single-qutrit","observables"]
docstr: Test that using bad index values throws the appropriate error
docstr_tok: ["Test","that","using","bad","index","values","throws","the","appropriate","error"]
code: def test_index_error(self, index):
      """Test that using bad index values throws the appropriate error"""
      with pytest.raises(
          ValueError,
          match="The index of a Gell-Mann observable must be an integer between 1 and 8 inclusive.",
      ):
          qml.GellMann(wires=0, index=index)
  
imports: import functools
  from unittest.mock import PropertyMock, patch
  import pytest
  import numpy
  from gate_data import GELL_MANN
  import pennylane
label_desc: Use image node_id 2 for calling the TestGellMann obj's underlying member method code with example usage: obj.test_index_error(index) without return types