text: import os
  import typing
  
  
  class EnvUtil(object):
      """An util helps get environment variable."""
  
      @staticmethod
      def get(key, defalut_value: typing.Optional[str] = None):
          val = os.environ.get(key)
          if val is None:
              val = defalut_value
          if val is None:
              raise ValueError("{} env variable is not set.".format(key))
          else:
              return val