code: def test_next_fast_len(self):
      for in_value in range(2000):
          out_value = cp_fft.next_fast_len(in_value)
          assert self._is_fast_len(out_value)
          for i in range(in_value, out_value):
              assert not self._is_fast_len(i)
  
imports: import unittest
  import cupyx.scipy.fft
label_desc: Use image node_id 2 for calling the TestNextFastLen obj's underlying member method code with example usage: obj.test_next_fast_len() without return types