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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def mass_enclosed(self, q, t=0.):
 """ Estimate the mass enclosed within the given position by assuming the potential is spherical. Parameters q : `~gala.dynamics.PhaseSpacePosition`, `~astropy.units.Quantity`, array_like Position(s) to estimate the enclossed mass. Returns ------- menc : `~astropy.units.Quantity` Mass enclosed at the given position(s). If the input position has shape ``q.shape``, the output energy will have shape ``q.shape[1:]``. """

        q = self._remove_units_prepare_shape(q)
        orig_shape, q = self._get_c_valid_arr(q)
        t = self._validate_prepare_time(t, q)

        # small step-size in direction of q
        h = 1E-3 # MAGIC NUMBER

        # Radius
        r = np.sqrt(np.sum(q**2, axis=1))

        epsilon = h*q/r[:, np.newaxis]

        dPhi_dr_plus = self._energy(q + epsilon, t=t)
        dPhi_dr_minus = self._energy(q - epsilon, t=t)
        diff = (dPhi_dr_plus - dPhi_dr_minus)

        if isinstance(self.units, DimensionlessUnitSystem):
            Gee = 1.
        else:
            Gee = G.decompose(self.units).value

        Menc = np.abs(r*r * diff / Gee / (2.*h))
        Menc = Menc.reshape(orig_shape[1:])

        sgn = 1.
        if 'm' in self.parameters and self.parameters['m'] < 0:
            sgn = -1.

        return sgn * Menc * self.units['mass']