What was the change in balances at the end of period between 2018 and 2019?
{"Balances at beginning of period": {"2019": 1856, "2018": 1748}, "Additions from acquisition": {"2019": 1884, "2018": 416}, "Additions - charged to expense": {"2019": 4207, "2018": 109}, "Deductions - write-offs, net of recoveries": {"2019": -202, "2018": -417}, "Balances at end of period": {"2019": 7745, "2018": 1856}}
balance_end_2019 = df["Balances at end of period"]["2019"]
balance_start_2019 = df["Balances at beginning of period"]["2019"]
answer = balance_end_2019 - balance_start_2019