def _updateCompleterDict(completers, cdict, regex=None):
        """Merges ``cdict`` into ``completers``. In the event that a key
        in cdict already exists in the completers dict a ValueError is raised
        iff ``regex`` false'y. If a regex str is provided it and the duplicate
        key are updated to be unique, and the updated regex is returned.
        """
        for key in cdict:
            if key in completers and not regex:
                raise ValueError(f"Duplicate completion key: {key}")

            if key in completers:
                uniq = "_".join([key, str(uuid.uuid4()).replace("-", "")])
                regex = regex.replace(f"P<{key}>", f"P<{uniq}>")
                completers[uniq] = cdict[key]
            else:
                completers[key] = cdict[key]

        return regex
Merges ``cdict`` into ``completers``. In the event that a key
        in cdict already exists in the completers dict a ValueError is raised
        iff ``regex`` false'y. If a regex str is provided it and the duplicate
        key are updated to be unique, and the updated regex is returned.