@staticmethod
def getMarketPrefix(stock_code):
    """Get the market code prefix from stock code."""
    assert type(stock_code) == str
    if stock_code.startswith('000'):
        return 'sz'
    if stock_code.startswith('200'):
        return 'sz'
    if stock_code.startswith('002'):
        return 'sz'
    if stock_code.startswith('300'):
        return 'sz'
    if stock_code.startswith('600'):
        return 'sh'
    if stock_code.startswith('601'):
        return 'sh'
    if stock_code.startswith('603'):
        return 'sh'
    if stock_code.startswith('900'):
        return 'sh'
    return 'unknown'
