docs: def check_need_install():
      """Check if installed package are exactly the same to this one.
      By checking md5 value of all files.
      """
      need_install_flag = False
      for root, _, basename_list in os.walk(SRC):
          if os.path.basename(root) != "__pycache__":
              for basename in basename_list:
                  src = os.path.join(root, basename)
                  dst = os.path.join(root.replace(SRC, DST), basename)
                  if os.path.exists(dst):
                      if md5_of_file(src) != md5_of_file(dst):
                          return True
                  else:
                      return True
      return need_install_flag