How can I use GetPlan service in Python ?

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Hello!

I want to use make_plan service of move_base package in order to create a path towards a specified goal. How am i supposed to deal with this service in Python ?

    start = PoseStamped()
    start.header.seq = 0
    start.header.frame_id = "map"
    start.header.stamp = rospy.Time(0)
    start.pose.position.x = robot_x  #2.6
    start.pose.position.y = robot_y  #1.3

    Goal = PoseStamped()
    Goal.header.seq = 0
    Goal.header.frame_id = "map"
    Goal.header.stamp = rospy.Time(0)
    Goal.pose.position.x = goal_x  #-6.2
    Goal.pose.position.y = goal_y  #-3.0

    srv = GetPlan()
    srv.request.start = start
    srv.request.goal = Goal
    srv.request.tolerance = 1.5

I assume that in this way I can declare the robot's current position(start) and target's coordinates(goal) as presented here. In which way should I initialize the server so that i can obtain the path ? What's the crucial part that I have to add in my code?