未实现错误：急切模式不支持while_loop

解决方案

1. Replace tf.while_loop with a Python while loop inside a tf.function that uses tf.constant for bounds:
   @tf.function
   def my_loop(n):
       i = tf.constant(0)
       while i < n:
           # loop body
           i += 1
       return i
   result = my_loop(tf.constant(5))

2. Use tf.range and tf.map_fn for vectorized operations instead of explicit loops:
   @tf.function
   def my_fn(n):
       return tf.map_fn(lambda x: x*2, tf.range(n))
   result = my_fn(tf.constant(5))