class_docstr: Test errors raised by stoch_pulse_grad.
class_docstr_tok: ["Test","errors","raised","by","stoch_pulse_grad","."]
docstr: Test that an error is raised when attempting to differentiate a tape that measures a variance.
docstr_tok: ["Test","that","an","error","is","raised","when","attempting","to","differentiate","a","tape","that","measures","a","variance","."]
code: def test_raises_for_variance(self):
      """Test that an error is raised when attempting to differentiate a tape that measures a variance."""
      tape = qml.tape.QuantumScript(
          measurements=[
              qml.expval(qml.PauliX(2)),
              qml.var(qml.PauliZ(0)),
          ]
      )
      with pytest.raises(
          ValueError,
          match="Computing the gradient of variances with the stochastic",
      ):
          stoch_pulse_grad(tape)
  
imports: import warnings
  import copy
  import pytest
  import numpy
  import pennylane
  from pennylane.gradients.general_shift_rules import eigvals_to_frequencies, generate_shift_rule
  from pennylane.gradients.pulse_gradient import _parshift_and_integrate, _split_evol_ops, _split_evol_tape, stoch_pulse_grad
label_desc: Use image node_id 1 for calling the TestStochPulseGradErrors obj's underlying member method code with example usage: obj.test_raises_for_variance() without return types