Compatibility issue with urllib3

[JaeyongYoo]

We are using the following combination (rpyc+openapi+urllib3) for processing REST requests and ran into this error.

Traceback (most recent call last):
  File "/usr/local/lib/python3.11/site-packages/rpyc/core/protocol.py", line 359, in _dispatch_request
    res = self._HANDLERS[handler](self, *args)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/rpyc/core/protocol.py", line 837, in _handle_call
    return obj(*args, **dict(kwargs))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/cna/cna-nf_sim/nf_sim/lib/python3/openapi/rest.py", line 502, in POST
    return self.request("POST",
           ^^^^^^^^^^^^^^^^^^^^
  File "/usr/cna/cna-nf_sim/nf_sim/lib/python3/openapi/rest.py", line 315, in request
    r = self.pool_manager.request(method,
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/urllib3/_request_methods.py", line 121, in request
    return self.request_encode_body(
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/urllib3/_request_methods.py", line 196, in request_encode_body
    extra_kw: dict[str, typing.Any] = {"headers": HTTPHeaderDict(headers)}
                                                  ^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/urllib3/_collections.py", line 252, in __init__
    self.extend(headers)
  File "/usr/local/lib/python3.11/site-packages/urllib3/_collections.py", line 370, in extend
    for key, value in other:
        ^^^^^^^^^^
ValueError: too many values to unpack (expected 2)

After some debugging, the issue is due to the RPYC's custom type (iterable tuple) is not really supporting the unpacking with the following syntax

for key, value in other:

which is causing the error "Too many values to unpack" where the iterable tuple can be unpacked with single item.
You can check the urllib3 source code for this part here: https://github.com/urllib3/urllib3/blob/main/src/urllib3/_collections.py#L355

Would you be possible to resolve this issue?