text: """Import libraries."""
  from typing import List, Dict
  
  
  class Direction:
      """
      Direction.
  
      This class contains only constants for all possible directions.
      """
  
      UP: str = "up"
      DOWN: str = "down"
      LEFT: str = "left"
      RIGHT: str = "right"
      ALL: List[str] = [UP, DOWN, LEFT, RIGHT]
      REVERSE: Dict[str, str] = {
          UP: DOWN,
          DOWN: UP,
          RIGHT: LEFT,
          LEFT: RIGHT
      }
  