code: def pair(self):
          
          if self.set_val is not None:
              return self.env_name, self.set_val
          elif self.default_val is not None:
              return self.env_name, os.environ.get(self.env_name, self.default_val)
          else:
              return self.env_name, os.environ[self.env_name]
docs: Get the name and value for this environment variable