code: def addPos(self, dp_x=None, dy=None, dz=None):
          
          p = np.array(self.GetPosition())
          if dz is None:  # assume dp_x is of the form (x,y,z)
              self.SetPosition(p + dp_x)
          else:
              self.SetPosition(p + [dp_x, dy, dz])
          if self.trail:
              self.updateTrail()
          return self
docs: Add vector to current actor position.