docstr: Load ticker list from txt file
docstr_tok: ["Load","ticker","list","from","txt","file"]
code: def get_tickers_from_file(self, filename):
      """Load ticker list from txt file"""
      if not os.path.exists(filename):
          log.error("Ticker List file does not exist: %s", filename)
  
      tickers = []
      with io.open(filename, "r") as fd:
          for ticker in fd:
              tickers.append(ticker.rstrip())
      return tickers
  
file_path: backtrader/contrib/utils/influxdb-import.py
imports: import sys
  import os
  import io
  import logging
  import argparse
  import pandas
  from influxdb import DataFrameClient
  from influxdb.exceptions import InfluxDBClientError
label_desc: Use image node_id 3 for calling the InfluxDBTool obj's underlying member method code with example usage: obj.get_tickers_from_file(filename) and returns: tickers