class ModuleDict(nn.Module):
    def __init__(self, data=None):
        super().__init__()
        self._module_list = nn.ModuleList()
        self._module_idcs = {}
        self._items = {}
        self.__dict__['_save_params'] = {}
        if data is not None:
            if isinstance(data, dict):
                for key,value in data.items():
                    self[key] = value
            elif all(len(item)==2 for item in list_(data)):
                for key,value in list_(data):
                    self[key] = value

    def forward(self, *inputs, **kwargs):
        raise NotImplementedError

    def __setitem__(self, key, value):
        def _has_module(arg):
            if isinstance(arg, dict): return any(_has_module(arg[k]) for k in arg)
            return isinstance(arg, nn.Module)

        if key in self._items:
            del self[key]

        if isinstance(value, dict):
            if _has_module(value): self[key] = ModuleDict(value)
            else: self._items[key] = value
        elif isinstance(value, nn.Module):
            self._items[key] = value
            self._module_idcs[key] = len(self._module_list)
            self._module_list.append(value)
        else:
            self._items[key] = value
            self.__dict__['_save_params'][key] = value

    def __getitem__(self, key):
        if key in self._items:
            return self._items[key]
        raise KeyError('ModuleDict as no attribute `%s`' % key)

    def __delitem__(self, key):
        if isinstance(self[key], nn.Module):
            self._module_list[self._module_idcs[key]] = None
            del self._module_idcs[key]
        else:
            del self.__dict__['_save_params'][key]
        del self._items[key]

    def __repr__(self, root=True):
        return ('ModuleDict({%s})' if root else '{%s}') % ', '.join(
            ["'%s': %s" % (k, v.__repr__(False) if isinstance(v, ModuleDict) else v if not isinstance(v, nn.Module) \
                else v.__class__.__name__ + '()') for k,v in self.items()]
        )

    def __iter__(self):
        return iter(self._items)

    def items(self):
        return self._items.items()

    def keys(self):
        return self._items.keys()

    def init(self):
        return init_([mod for mod in self._module_list])