Method _copy_from

src/urllib3/_collections.py:428–431

(self, other: HTTPHeaderDict)

        return f"{type(self).__name__}({dict(self.itermerged())})"

    def _copy_from(self, other: HTTPHeaderDict) -> None:
        for key in other:
            val = other.getlist(key)
            self._container[key.lower()] = [key, *val]

    def copy(self) -> Self:
        clone = type(self)()