def _flatten_inst_regs(iterable):
    """Flatten an iterable of registers used in an instruction
    """
    for item in iterable:
        if isinstance(item, str):
            yield item
        elif isinstance(item, (tuple, list)):
            for x in _flatten_inst_regs(item):
                yield x
Flatten an iterable of registers used in an instruction
    
numba/core/byteflow.py