如何有条件地向Keras模型添加层？

from tensorflow.keras import layers

model = Sequential()
model.add(layers.Dense(64, activation='relu'))

model.pop()
model.add(layers.Dense(10, activation='softmax'))

from tensorflow.keras import layers, models

# 定义输入层
inputs = layers.Input(shape=(784,))

# 添加层
x = layers.Dense(64, activation='relu')(inputs)
x = layers.Dense(64, activation='relu')(x)
outputs = layers.Dense(10, activation='softmax')(x)

# 创建模型
model = models.Model(inputs=inputs, outputs=outputs)