Strips zeros while handling -, M, and empty strings

def remove_leading_zeros(num: str) -> str:
    """
    Strips zeros while handling -, M, and empty strings
    """
    if not num:
        return num
    if num.startswith('M'):
        ret = 'M' + num[1:].lstrip('0')
    elif num.startswith('-'):
        ret = '-' + num[1:].lstrip('0')
    else:
        ret = num.lstrip('0')
    return '0' if ret in ('', 'M', '-') else ret