def test_pwm_frequency_invalid_value_string(self):
     PWM.start("P9_14", 0)
     with pytest.raises(TypeError):
         PWM.set_frequency("P9_14", "11")
         PWM.cleanup()
 def test_pwm_freq_non_setup_key(self):
     with pytest.raises(ValueError):
         PWM.set_frequency("P9_15", 100)
         PWM.cleanup()                            
 def test_pwm_frequency_invalid_value_negative(self):
     PWM.start("P9_14", 0)
     with pytest.raises(ValueError):
         PWM.set_frequency("P9_14", -1)
         PWM.cleanup()