TypeError: float() argument must be a string or a number

edit

Hello, I follow this repo and want to combine it to my robot.

But when I try to get the rotation and convert it to Quaternion. I encounter the error below:

 cyc@cyc-X550JX:~$ rosrun gpd test_grasp.py 
[INFO] [1558753204.760210]: Start to get grasp data...
[INFO] [1558753209.430311]: Received 1 grasps.
[x: 0.527165424825
y: 0.842580358548
z: 0.110249509106
 x: 0.849633644563
y: -0.524891291709
z: -0.0511057914036
 x: 0.0148082712001
y: 0.120612898469
z: -0.992589161651]
Traceback (most recent call last):
  File "/home/cyc/catkin_ws/src/gpd/src/test_grasp.py", line 74, in <module>
    qua_R = tf.transformations.quaternion_from_matrix(R)
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/tf/transformations.py", line 1206, in quaternion_from_matrix
    M = numpy.array(matrix, dtype=numpy.float64, copy=False)[:4, :4]
**TypeError: float() argument must be a string or a number**

Here is my code and the GraspConfig information:

#!/usr/bin/env python
import rospy
import sys
import tf
import numpy as np
from gpd.msg import GraspConfigList
from tf.transformations import quaternion_from_matrix
from geometry_msgs.msg import Pose
from geometry_msgs.msg import PoseStamped 

grasps = []

def callback(msg):
    global grasps
    grasps = msg.grasps

# Create a ROS node.
rospy.init_node('get_grasps')
rospy.loginfo('Start to get grasp data...')

# Subscribe to the ROS topic that contains the grasps.
sub = rospy.Subscriber('/detect_grasps/clustered_grasps', GraspConfigList, callback)

# Wait for grasps to arrive.
rospy.sleep(1)

while not rospy.is_shutdown():    
    if len(grasps) > 0:
        top_grasp = grasps[0] # grasps are sorted in descending order by score.
        rospy.loginfo('Received %d grasps.', len(grasps))

        R = (top_grasp.approach, top_grasp.binormal, top_grasp.axis)
        R = np.asarray(R)
        print(R)

        qua_R = tf.transformations.quaternion_from_matrix(R)
        print qua_R

        break   

rospy.spin()

Hope you guys can help me, thanks a lot!