Checks if the specified bank contains the specified key.

def contains(bank, key):
    '''
    Checks if the specified bank contains the specified key.
    '''
    _init_client()
    query = "SELECT COUNT(data) FROM {0} WHERE bank='{1}' " \
        "AND etcd_key='{2}'".format(_table_name, bank, key)
    cur, _ = run_query(client, query)
    r = cur.fetchone()
    cur.close()
    return r[0] == 1