tf2_ros buffer transform PointStamped?

edit

I'd like to transform a PointStamped using a python tf2_ros.Buffer, but so far I'm only getting type exceptions. The following example a point with only a y component is supposed to be trivially transformed into the frame it is already in:

#!/usr/bin/env python

import rospy
import sys
import tf2_ros

from geometry_msgs.msg import PointStamped

if __name__ == '__main__':
    rospy.init_node('transform_point_tf2')
    tf_buffer = tf2_ros.Buffer()
    tf_listener = tf2_ros.TransformListener(tf_buffer)

    rospy.sleep(1.0)
    pt = PointStamped()
    pt.header.stamp = rospy.Time.now()
    pt.header.frame_id = "map"
    pt.point.x = 0.0
    pt.point.y = 1.0
    pt.point.z = 0.0

    try:
        pt2 = tf_buffer.transform(pt, "map")
    except:  # tf2_ros.buffer_interface.TypeException as e:
        e = sys.exc_info()[0]
        rospy.logerr(e)
        sys.exit(1)

    rospy.loginfo(pt2)

This results in:

[ERROR] [/transform_point_tf2] [./transform_point_tf2.py]:[27] [<class 'tf2_ros.buffer_interface.TypeException'>]

If PointStamped isn't the right type, then what type can I use?

To do this manually I'm currently doing this:

            trans = self.tf_buffer.lookup_transform("map", target_frame,
                                                        rospy.Time())

            quat = [trans.transform.rotation.x,
                    trans.transform.rotation.y,
                    trans.transform.rotation.z,
                    trans.transform.rotation.w]
            mat = tf.transformations.quaternion_matrix(quat)
            pt_np = [pt.point.x,
                     pt.point.y,
                     pt.point.z,
                     1.0]
            pt_in_map_np = numpy.dot(mat, pt_np)

            pt_in_map.x = pt_in_map_np[0]
            pt_in_map.y = pt_in_map_np[1]
            pt_in_map.z = pt_in_map_np[2]