old_contents: import os
  
  TESTING_API_KEY = 'YourApiKeyToken'
  ETHERSCAN_API_KEY = os.environ.get('ETHERSCAN_API_KEY', TESTING_API_KEY)
  
new_contents: import os
  
  HOME_DIR = os.path.expanduser('~')
  CONFIG_FILE = '.pyetherscan.ini'
  PATH = os.path.join(HOME_DIR, CONFIG_FILE)
  TESTING_API_KEY = 'YourApiKeyToken'
  
  if os.path.isfile(PATH):
      from configparser import ConfigParser
      config = ConfigParser()
      config.read(PATH)
      ETHERSCAN_API_KEY = config['Credentials']['ETHERSCAN_API_KEY']
  
  else:
      ETHERSCAN_API_KEY = os.environ.get('ETHERSCAN_API_KEY', TESTING_API_KEY)
  
subject: Add support for a configuration file