code: func AsErrorList(err error) ErrorList {
  	if list, ok := err.(ErrorList); ok {
  		return list
  	}
  	return ErrorList{err}
  }
docs: // AsErrorList checks if err is already an ErrorList
  // and returns it if this is the case.
  // Else an ErrorList with err as element is created.
  // Useful if a function potentially returns an ErrorList as error
  // and you want to avoid creating nested ErrorLists.