class_docstr: Test for validation and exceptions
docstr: Test that an error is raised if the qfunc has no quantum operations
  (e.g., it is not a qfunc)
docstr_tok: ["Test","that","an","error","is","raised","if","the","qfunc","has","no","quantum","operations","(","e.g.",",","it","is","not","a","qfunc",")"]
code: def test_empty_qfunc(self):
      """Test that an error is raised if the qfunc has no quantum operations
      (e.g., it is not a qfunc)"""
  
      @qml.op_transform
      def my_transform(op):
          return op.name
  
      def qfunc(x):
          return x**2
  
      with pytest.raises(
          OperationTransformError,
          match="Quantum function contains no quantum operations",
      ):
          my_transform(qfunc)(0.5)
  
imports: import pytest
  import pennylane
  from pennylane import numpy
  from pennylane.transforms.op_transforms import OperationTransformError
label_desc: Use image node_id 4 for calling the TestValidation obj's underlying member method code with example usage: obj.test_empty_qfunc() and returns: op, unknown