md_stock_symbol returns all stock symbols by exchange
md_stock_symbol(exchange = NULL, ...)the available stock exchanges are sse, szse, hkex, amex, nasdaq, nyse.
ignored parameters
if (FALSE) {
# get stock symbols in a stock exchange
## specify the exchanges
ex_syb1 = md_stock_symbol(exchange = c('sse', 'szse'))
## choose exchanges interactivly
ex_syb2 = md_stock_symbol()
# constituent stock symbol of index
dtidx = md_stock_symbol(index = c('930050', '000300', '000905', '000852'))
}