code: def test_auto_vel_dont_overwrite():
      t = dynamicsymbols._t
      q1, q2, u1 = dynamicsymbols("q1, q2, u1")
      N = ReferenceFrame("N")
      P = Point("P1")
      P.set_vel(N, u1 * N.x)
      P1 = Point("P1")
      P1.set_pos(P, q2 * N.y)
      assert P1.vel(N) == q2.diff(t) * N.y + u1 * N.x
      assert P.vel(N) == u1 * N.x
      P1.set_vel(N, u1 * N.z)
      assert P1.vel(N) == u1 * N.z
  
imports: from sympy.physics.vector import dynamicsymbols, Point, ReferenceFrame
  from sympy.testing.pytest import raises, ignore_warnings
  import warnings
label_desc: Use image node_id 11 for calling a global function with example usage: test_auto_vel_dont_overwrite() without return types