[Mod] clear previously loaded history data
[Mod] clear previously loaded history data

bigdig/vnpy,msincenselee/vnpy,bigdig/vnpy,msincenselee/vnpy,msincenselee/vnpy,bigdig/vnpy,andrewchenshx/vnpy,vnpy/vnpy,msincenselee/vnpy,andrewchenshx/vnpy,andrewchenshx/vnpy,andrewchenshx/vnpy,andrewchenshx/vnpy,bigdig/vnpy,vnpy/vnpy