def _get_payload(msg: email.message.Message, source: Union[bytes, str]) -> str:
    """Get the body of the message."""
    # If our source is a str, then our caller has managed encodings for us,
    # and we don't need to deal with it.
    if isinstance(source, str):
        payload: str = msg.get_payload()
        return payload
    # If our source is a bytes, then we're managing the encoding and we need
    # to deal with it.
    else:
        bpayload: bytes = msg.get_payload(decode=True)
        try:
            return bpayload.decode("utf8", "strict")
        except UnicodeDecodeError:
            raise ValueError("payload in an invalid encoding")
Get the body of the message.
product/runtime/src/main/python/pkg_resources/_vendor/packaging/metadata.py