Parametrization cannot be parametrized

[albanD]

The Parametrization that contains the original Tensor is not traversing itself properly during the forward.
In particular here:

pytorch/torch/nn/utils/parametrize.py

Line 265 in 96cb05b

for module in list(self._modules.values())[1:]:

We use all the _modules even the ones that are not indexed by integers.
This prevent parametrization of parametrization because it would add a parametrizations submodule to this and the forward would try to traverse it.

cc @albanD @mruberry @jbschlosser @walterddr

[albanD]

Note that the fix above is only for the forward. We should double check and test that the right_inverse method also works fine.