Fix typing error of torch/nn/modules/container.pyi.in (#33686)

Summary:
* `Sequential` has `__iter__` method, but type stub doesn't
* `ModuleList.__getitem__` returns `Module`, but type stub doesn't
* Type stub says `ParameterList` has `insert` method, but actual `ParameterList` doesn't
* `ParameterDict.__getitem__` should returns `Parameter`
* `ParameterList` and `ParameterDict` have `extra_repr` methods

 ---

torch/nn/modules/container.py: https://github.com/pytorch/pytorch/blob/master/torch/nn/modules/container.py
torch/nn/modules/container.pyi.in: https://github.com/pytorch/pytorch/blob/master/torch/nn/modules/container.pyi.in
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33686

Differential Revision: D20086730

Pulled By: ngimel

fbshipit-source-id: a8271489417461c67ff84a239c4cd96c3aa17b5c
diff --git a/torch/nn/modules/container.pyi.in b/torch/nn/modules/container.pyi.in
index 82e1be3..41f55ea 100644
--- a/torch/nn/modules/container.pyi.in
+++ b/torch/nn/modules/container.pyi.in
@@ -31,6 +31,8 @@
 
     def __len__(self) -> int: ...
 
+    def __iter__(self) -> Iterator[Module]: ...
+
     def forward(self, input: Tensor) -> Tensor: ...
 
 
@@ -63,7 +65,7 @@
 class ModuleDict(Module):
     def __init__(self, modules: Optional[Mapping[str, Module]] = ...) -> None: ...
 
-    def __getitem__(self, key: str): ...
+    def __getitem__(self, key: str) -> Module: ...
 
     def __setitem__(self, key: str, module: Module) -> None: ...
 
@@ -107,17 +109,17 @@
 
     def __iadd__(self: T, parameters: Iterable[Parameter]) -> T: ...
 
-    def insert(self, index: int, parameter: Parameter) -> None: ...
-
     def append(self: T, parameter: Parameter) -> T: ...
 
     def extend(self: T, parameters: Iterable[Parameter]) -> T: ...
 
+    def extra_repr(self) -> str: ...
+
 
 class ParameterDict(Module):
     def __init__(self, parameters: Optional[Mapping[str, Parameter]] = ...) -> None: ...
 
-    def __getitem__(self, key: str): ...
+    def __getitem__(self, key: str) -> Parameter: ...
 
     def __setitem__(self, key: str, param: Parameter) -> None: ...
 
@@ -140,3 +142,5 @@
     def values(self) -> Iterable[Parameter]: ...
 
     def update(self, parameters: Mapping[str, Parameter]) -> None: ...
+
+    def extra_repr(self) -> str: ...