I was going through the documentation and think I might have stumbled upon some incomplete code on the following link:

https://www.backtrader.com/docu/observers-and-statistics/observers-and-statistics.html#observer-implementation

from __future__ import (absolute_import, division, print_function,
                        unicode_literals)

import argparse
import datetime
import os.path
import time
import sys


import backtrader as bt
import backtrader.feeds as btfeeds
import backtrader.indicators as btind


class MyStrategy(bt.Strategy):
    params = (('smaperiod', 15),)

    def log(self, txt, dt=None):
        ''' Logging function fot this strategy'''
        dt = dt or self.data.datetime[0]
        if isinstance(dt, float):
            dt = bt.num2date(dt)
        print('%s, %s' % (dt.isoformat(), txt))

    def __init__(self):