想通过数组定义网架结构，但是神经网络层不可以放在数组里面吗？

xframe = [1,2,1]
class LineNet(nn.Layer):
    def __init__(self):
        super(LineNet, self).__init__()
        #self.fcs = [nn.Linear(in_features=xframe[i], out_features=xframe[i+1]) for i in range(len(xframe)-1)]#'''
        self.fcs = [ nn.Linear(1, 1) ]

    def forward(self, x, label=None):
        x = paddle.nn.functional.tanh(self.fcs[0](x))
        return x

运行就报错：

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
/tmp/ipykernel_161/1595878955.py in 
     88         loss = nn.functional.mse_loss(out, label)
     89         loss.backward()
---> 90         opt.step()
     91         opt.clear_grad()
     92         epochidx += 1

 in step(self)

/opt/conda/envs/python35-paddle120-env/lib/python3.7/site-packages/paddle/fluid/dygraph/base.py in __impl__(func, *args, **kwargs)
    297         def __impl__(func, *args, **kwargs):
    298             with _switch_tracer_mode_guard_(is_train=False):
--> 299                 return func(*args, **kwargs)
    300 
    301         return __impl__(func)

 in step(self)

/opt/conda/envs/python35-paddle120-env/lib/python3.7/site-packages/paddle/fluid/wrapped_decorator.py in __impl__(func, *args, **kwargs)
     23     def __impl__(func, *args, **kwargs):
     24         wrapped_func = decorator_func(func)
---> 25         return wrapped_func(*args, **kwargs)
     26 
     27     return __impl__

/opt/conda/envs/python35-paddle120-env/lib/python3.7/site-packages/paddle/fluid/framework.py in __impl__(*args, **kwargs)
    432         assert _non_static_mode(
    433         ), "We only support '%s()' in dynamic graph mode, please call 'paddle.disable_static()' to enter dynamic graph mode." % func.__name__
--> 434         return func(*args, **kwargs)
    435 
    436     return __impl__

/opt/conda/envs/python35-paddle120-env/lib/python3.7/site-packages/paddle/optimizer/optimizer.py in step(self)
   1208         """
   1209 
-> 1210         if not isinstance(self._param_groups[0], dict):
   1211             params_grads = []
   1212             for param in self._param_groups:

IndexError: list index out of range