Convert a python code to Keras custom layer

Convert attached file into a custom layer in Keras.
It should work smoothly in below code. I can provide you the whole code once the freelancer is selected.

model.add(Conv2D(64, (3, 3), padding="same"))
model.add(Activation("relu"))
model.add(BatchNormalization(axis=chanDim))
model.add(Conv2D(64, (3, 3), padding="same"))
model.add(Activation("relu"))
model.add(BatchNormalization(axis=chanDim))
model.add(AvgPooling2D(pool_size=(2, 2)))
model.add(Dropout(0.25))

# first (and only) set of FC => RELU layers
model.add(Flatten())
model.add(Dense(512))
model.add(Activation("relu"))
model.add(BatchNormalization())
model.add(Dropout(0.5))
# softmax classifier
model.add(Dense(classes))
model.add(Activation("softmax"))
model.summary()