如何实现距离转换的问题

def convert_distance(distance, unit):
    # 转换逻辑
    return converted_distance, converted_unit

def convert_distance(distance, unit):
    conversions = {
        'm': {
            'km': distance / 1000,
            'mile': distance * 0.000621371,
            'foot': distance * 3.28084,
            'yard': distance * 1.09361
        },
        'km': {
            'm': distance * 1000,
            'mile': distance * 0.621371,
            'foot': distance * 3280.84,
            'yard': distance * 1093.61
        },
        'mile': {
            'm': distance * 1609.34,
            'km': distance * 1.60934,
            'foot': distance * 5280,
            'yard': distance * 1760
        },
        # 其他单位的转换关系
    }

    converted_distance = conversions[unit]['km']
    converted_unit = 'km'

    return converted_distance, converted_unit