<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def __root_path(self):

 """ Just checks the root path if set """

        if self.root_path is not None:
            if os.path.isdir(self.root_path):
                sys.path.append(self.root_path)
                return
            raise RuntimeError('EverNode requires a valid root path.'
                               ' Directory: %s does not exist'
                               % (self.root_path))