md_moneycn query benchmark rates from chinamoney.com.cn.
md_moneycn(symbol = NULL, date_range = "3y", from = NULL, to = Sys.Date(), print_step = 1L)
benchmarks, available values including shibor, lpr, br, rmbx. Default is NULL,
date range. Available value includes '1m'-'11m', 'ytd', 'max' and '1y'-'ny'. Default is 3y.
the start date. Default is NULL. If it is NULL, then calculate using date_range and end date.
the end date. Default is the current date.
a non-negative integer, which will print symbol name by each print_step iteration. Default is 1L.