Argument must be a dense tensor: range(0, 3) - got shape [3], but wanted []
tensorflow遇到问题：
ValueError: Tried to convert 't' to a tensor and failed. Error: Argument must be a dense tensor: range(0, 3) - got shape [3], but wanted [].
原因是python2转python3后，range（）返回的shape是range（0，3）而不再是list。
需要将models/research/object_detection/utils/learning_schedules.py里的：
rate_index = tf.reduce_max(tf.where(tf.greater_equal(global_step, boundaries),
range(num_boundaries),
[0] * num_boundaries))修改成：
rate_index = tf.reduce_max(tf.where(tf.greater_equal(global_step, boundaries),
list(range(num_boundaries)),
[0] * num_boundaries)