Hi! I got the following error ValueError: optimizer got an empty parameter list when I run the code containing the following classes:
class Mass_and_v():
    def __init__(self, param):
        self.parameter = param
        
    # get_mass + v_circ_tot
    def __call__(self, x):
        ener_f = 56.0 # keV
        r, mass = rar.model(self.parameter[3:].detach().numpy(),ener_f)
        isnan = np.argwhere(np.isnan(mass))
        if (np.any(isnan)):
            np.argwhere(np.isnan(mass))[0][0]
        else:
            k = -1
        r_s = r[0:k]
        mass_s = mass[0:k]
        mass_spline = InterpolatedUnivariateSpline(r_s, mass_s, k=4)
        r_max = np.amax(r_s)
        if x <= r_max:
            return np.sqrt(v_circ_b(x,self.parameter[0].detach().numpy())**2 + v_circ_MN(x,self.parameter[1:3].detach().numpy())**2 + G_u*mass_spline(x)/x)
        else:
            return np.sqrt(v_circ_b(x,self.parameter[0].detach().numpy())**2 + v_circ_MN(x,self.parameter[1:3].detach().numpy())**2 + G_u*mass_spline(r_max)/x)

class FitModel(nn.Module):
    def __init__(self):
        super(FitModel, self).__init__()
        self.nonlinear_stack = Mass_and_v(param_t)
        
    def forward(self, x):
        output = self.nonlinear_stack(x)
        return output

I got the error when the code comes to the line
optimizer = torch.optim.Adam(model.parameters(), lr=eta, eps=1e-08, weight_decay=0, amsgrad=False)

I hope someone can help me. Thank you so much in advance