AttributeError: PgStatStore instance has no attribute 'append'

[tuhaolam]

File "pg-stat.py", line 355, in init
s_db.append("deadlocks")
AttributeError: PgStatStore instance has no attribute 'append'
->%
s_db is '<main.PgStatStore instance at 0x7f8d4e8fc9e0>', not list, cannot run append.