code: def init_from_env(self):
          
  
          if 'default' in self.node:
              env_var = self.__to_env_var__().upper()
              if self.has_value():
                  env_val = self.node['value']
              else:
                  env_val = self.node['default']
              env_val = os.getenv(env_var, to_yaml(env_val))
              try:
                  self.node['value'] = yaml.load(
                      str(env_val), Loader=ConfigLoader)
              except ValueError:
                  self.node['value'] = env_val
          else:
              if isinstance(self.node, dict):
                  for k in self.node:
                      self[k].init_from_env()
docs: Initialize this node from environment.
  
          If we're a leaf node, i.e., a node containing a dictionary that
          consist of a 'default' key, compute our env variable and initialize
          our value from the environment.
          Otherwise, init our children.