df = BDH("AAPL US EQUITY", "PX_LAST", "20150101", "20150103")
df = BDP("AAPL US EQUITY", "PX_LAST")
df = BDS("AAPL US EQUITY", "DVD_HIST_ALL")
BCOM_wrapper is a wrapper of Bloomberg COM API
BCOM_test demonstrates example usages of BCOM_wrapper
tester_referenceData is like BDP
tester_bulkReferenceData is like BDS
tester_historicalData is like BDH