简答题 补充以下代码,实现如上图所示的单隐层神经网络模型的构建,实现一个二分类问题.(网络中隐含层神经元使用sigmoid激活函数). W1 = tf.Variable( ,mean=0.0, stddev=1.0, dtype=tf.float32)) B1 = tf.Variable( ,dtype = tf.float32) W2 = tf.Variable( ,mean=0.0, stddev=1.0, dtype=tf.float32)) B2 = W = [W1, W2] B = [B1, B2] def model(x, w, b): x = x = x = pred = return pred