Error converting yolov4 custom keras model to tensorflow model

[prateek09101996]

eras\activations.py", line 573, in get
return deserialize(identifier)
File "H:\repo\keras_to_tensorflow-master\keras_to_tensorflow-master\env-tf1.15.0\lib\site-packages\tensorflow\python\util\dispatch.py", line 201, in wrapper
return target(*args, **kwargs)
File "H:\repo\keras_to_tensorflow-master\keras_to_tensorflow-master\env-tf1.15.0\lib\site-packages\tensorflow\python\keras\activations.py", line 536, in deserialize
printable_module_name='activation function')
File "H:\repo\keras_to_tensorflow-master\keras_to_tensorflow-master\env-tf1.15.0\lib\site-packages\tensorflow\python\keras\utils\generic_utils.py", line 378, in deserialize_keras_object
'Unknown ' + printable_module_name + ': ' + object_name)
ValueError: Unknown activation function: mish