tensorflow的feed（注入）数据类型

import tensorflow as tf
import numpy as np

a=tf.placeholder(tf.float32,shape=None)
b=tf.placeholder(tf.float32,shape=None)

z=tf.matmul(a,b)

with tf.Session() as sess:
    sess.run(tf.global_variables_initializer())
    z=sess.run(z, feed_dict={a: np.ones([2,3]), b:np.ones([3,4])})
    print(z)

feed的时候不能用注入Tensor