code: def q(self, x, q0):
          
          y1_0 = q0
          y0_0 = 0
          y0   = [y0_0, y1_0]
  
          y = _sp.integrate.odeint(self._func, y0, x, Dfun=self._gradient, rtol=self.rtol, atol=self.atol)
  
          return y[:, 1]
docs: Numerically solved trajectory function for initial conditons :math:`q(0) = q_0` and :math:`q'(0) = 0`.