def hexstr_if_str(to_type, hexstr_or_primitive):
    """
    Convert to a type, assuming that strings can be only hexstr (not unicode text)

    @param to_type is a function that takes the arguments (primitive, hexstr=hexstr, text=text),
        eg~ to_bytes, to_text, to_hex, to_int, etc
    @param text_or_primitive in bytes, str, or int.
    """
    if isinstance(hexstr_or_primitive, str):
        (primitive, hexstr) = (None, hexstr_or_primitive)
        if remove_0x_prefix(hexstr) and not is_hex(hexstr):
            raise ValueError(
                "when sending a str, it must be a hex string. Got: {0!r}".format(
                    hexstr_or_primitive,
                )
            )
    else:
        (primitive, hexstr) = (hexstr_or_primitive, None)
    return to_type(primitive, hexstr=hexstr)