我如何实现一个控制结构来绕过keras中的某些层？

from tensorflow.keras.models import Model
from tensorflow.keras.layers import Input, Dense, Dropout

input_layer = Input(shape=(input_shape,))

layer_to_bypass = Dense(units=64, activation='relu')(input_layer)

if bypass_condition:
    bypass_layer = Dropout(rate=0.5)(layer_to_bypass)
else:
    bypass_layer = layer_to_bypass

output_layer = Dense(units=num_classes, activation='softmax')(bypass_layer)

model = Model(inputs=input_layer, outputs=output_layer)

model.compile(optimizer='adam', loss='categorical_crossentropy', metrics=['accuracy'])
model.fit(x_train, y_train, batch_size=batch_size, epochs=epochs, validation_data=(x_val, y_val))