code: def added_env_paths(env_vars, env=None):
      
      if not env_vars:
          return None
  
      if not env:
          env = dict(os.environ)
  
      result = dict(env)
      for env_var, paths in env_vars.items():
          separator = paths[0]
          paths = paths[1:]
          current = env.get(env_var, "")
          current = [x for x in current.split(separator) if x]
  
          added = 0
          for path in paths.split(separator):
              if path not in current:
                  added += 1
                  current.append(path)
  
          if added:
              result[env_var] = separator.join(current)
  
      return result
docs: :param dict|None env_vars: Env vars to customize
      :param dict env: Original env vars