text: import math
  import os
  
  
  TOKEN_WIKI_URL = 'https://github.com/tmrowco/electricitymap-contrib/wiki/Create-tokens'
  
  def get_token(token):
      """Get a token from the environment variables
  
      Raises:
          Exception: if the token variable does not exists or if its value is null
      """
      if not os.environ.get(token):
          raise Exception(
              f'Environment variable {token} not found !\n'
              f'Please visit {TOKEN_WIKI_URL}#{token} for more information about how to create '
              'tokens.')
      return os.environ[token]
  
  def sum_production_dicts(prod1: dict, prod2: dict()):
      """
      Sum two productions dictionnaries. For a production mode key, if both
      values are None, the result is None. Else, the None is replaced by zero
      """
      to_return = prod1.copy()
      for prod_name, value2 in prod2.items():
          value1 = to_return.get(prod_name)
          if value1 is None and value2 is None:
              continue
          to_return[prod_name] = (value1 or 0) + (value2 or 0)
      return to_return
  
  
  def nan_to_zero(v):
      if math.isnan(v):
          return 0
      return v
  