how do i can put a point inside a 3d mesh

[alialzobani]

import pyvista
import pyvista as pv
from pyvista import examples
import numpy as np
from pyvista.examples import planefile

class Picker:
def init(self, plotter, mesh):
self.plotter = plotter
self.mesh = mesh
self._points = []

@property
def points(self):
    """To access all th points when done."""
    return self._points

def __call__(self, *args):
    picked_pt = np.array(self.plotter.pick_mouse_position())

    #picked_pt[2]=0
    print(picked_pt)

    direction = picked_pt - self.plotter.camera_position[0]
    direction = direction / np.linalg.norm(direction)
    start = picked_pt - 1000 * direction
    end = picked_pt + 10000 * direction
    point, ix = self.mesh.ray_trace(start, end, first_point=True)

    if len(point) > 0:
        self._points.append(point)
        w = p.add_mesh(pv.Sphere(radius=3.0 , center=picked_pt),
                       color='red')
    return

mesh = examples.load_airplane()

p = pv.Plotter(notebook=False)
p.add_mesh(mesh, show_edges=True, color='w')

picker = Picker(p, mesh)
p.track_click_position(picker, side='right')
p.add_text('Use right mouse click to pick points')
p.show_axes()

p.show()

[alialzobani]

i can using this code to put points on the outside of the mesh, put i want to put points inside the mesh too.
thanks for our helpe