加载的.pb文件的tf.get\集合(tf.GraphKeys.GLOBAL\变量)是empy

.pb 文件,但由于某种原因它是空的。

import tensorflow as tf

tf_model_path = './tf_coreml_ssd_resources/ssd_mobilenet_v1_android_export.pb'

with open(tf_model_path, 'rb') as f:
    serialized = f.read()

tf.reset_default_graph()

original_gdef = tf.GraphDef()
original_gdef.ParseFromString(serialized)

# V1
with tf.Graph().as_default() as g:
    print('type(g)', type(g)) # type(g) <class 'tensorflow.python.framework.ops.Graph'>

    tf.import_graph_def(original_gdef, name='')

    model_vars = tf.get_collection(tf.GraphKeys.GLOBAL_VARIABLES)
    print('type(model_vars)', type(model_vars))
    print('model_vars', model_vars)

# V2
graph = tf.import_graph_def(original_gdef, name='')

print('type(graph)', type(graph)) # why type(graph) <class 'NoneType'> ?

model_vars = tf.get_collection(tf.GraphKeys.GLOBAL_VARIABLES)
print('type(model_vars)', type(model_vars))
print('model_vars', model_vars)

还有为什么万一我 type(graph) <class 'NoneType'>