class_docstr: Test Evolution(Exp) class that takes a parameter x and a generator G and defines an evolution exp(ixG)
docstr: Test that has_generator returns True if the coefficient is purely imaginary.
docstr_tok: ["Test","that","has_generator","returns","True","if","the","coefficient","is","purely","imaginary","."]
code: def test_has_generator_true(self):
      """Test that has_generator returns True if the coefficient is purely imaginary."""
      U = Evolution(qml.PauliX(0), 3)
      assert U.has_generator is True
  
imports: import pytest
  import pennylane
  from pennylane import numpy
  from pennylane.ops.op_math import Evolution, Exp
label_desc: Use image node_id 3 for calling the TestEvolution obj's underlying member method code with example usage: obj.test_has_generator_true() without return types