class_docstr: Test the utility function _nonzero_coeffs_and_words.
class_docstr_tok: ["Test","the","utility","function","_nonzero_coeffs_and_words","."]
docstr: Test that the precision keyword argument atol is used correctly.
docstr_tok: ["Test","that","the","precision","keyword","argument","atol","is","used","correctly","."]
code: def test_atol(self):
      """Test that the precision keyword argument atol is used correctly."""
      atols = [1e-8, 1e-4, 1e-1]
      # With the following coefficients, different rows will be considered to vanish
      # for the different tolerances set above.
      coeffs = (np.array(atols), np.array(atols) * 2)
      for i, atol in enumerate(atols):
          new_coeffs, words = _nonzero_coeffs_and_words(
              coeffs, 1, atol=atol / 10
          )
          assert len(new_coeffs) == 2
          assert all(len(c) == 3 - i for c in new_coeffs)
          assert words == ["X", "Y", "Z"][i:]
      new_coeffs, words = _nonzero_coeffs_and_words(coeffs, 1, atol=1.0)
      assert new_coeffs == [[], []]
      assert words == []
  
imports: import copy
  import pytest
  import numpy
  import pennylane
  from pennylane import numpy
  from pennylane.ops.qubit.special_unitary import pauli_basis_matrices, pauli_basis_strings
  from pennylane.math import expand_matrix
  from pennylane.gradients.pulse_gradient_odegen import _generate_tapes_and_coeffs, pulse_odegen, _insert_op, _nonzero_coeffs_and_words, _one_parameter_generators, _one_parameter_paulirot_coeffs, _parshift_and_contract
label_desc: Use image node_id 4 for calling the TestNonzeroCoeffsAndWords obj's underlying member method code with example usage: obj.test_atol() without return types