code: def _is_fast_len(self, n):
      if n == 0:
          return True
      for p in (2, 3, 5, 7):
          while n % p == 0:
              n //= p
      return n == 1
  
imports: import unittest
  import cupyx.scipy.fft
label_desc: Use image node_id 1 for calling the TestNextFastLen obj's underlying member method code with example usage: obj._is_fast_len(n) and returns: unknown, True