pfb_decimator_ccf(13): insufficient connected input ports (5 needed, 1 connected)

Hi, all I try to re-structure the osmo-tetra to work with GNU Radio 3.7. The osmo-tetra is based on GNU Radio 3.6. The original code has tuner, resampler, demodulater three modules which connected sequentially. The resampler is based on function pfb_decimator_ccf which changes from 3.6 to 3.7. The pfb_decimator_ccf only take single parameter decimation, which changes in 3.7, After reading the manual of 3.7, I made following changes to the python script : Add a low-pass filter " taps = filter.firdes.low_pass_2(1, fs, options.low_pass, options.low_pass * 0.2, attenuation_dB=ATT, window=filter.firdes.WIN_BLACKMAN_hARRIS) " Change "self.resamp = blks2.pfb_decimator_ccf(int(rerate)) " to " self.resamp = filter.pfb_decimator.ccf(int(rerate), taps, 0) " But error still occurs when connecting modules " self.connect(self.src, self.tuner, self.resamp, self.demod, self.output) " : Traceback (most recent call last): File "./osmosdr-tetra_demod_fft.py", line 264, in <module> tb.Run(True) File "/usr/local/lib/python2.7/dist-packages/grc_gnuradio/wxgui/top_block_gui.py", line 82, in Run self.Start(start, max_nouts) File "/usr/local/lib/python2.7/dist-packages/grc_gnuradio/wxgui/top_block_gui.py", line 73, in Start self.start() File "/usr/local/lib/python2.7/dist-packages/gnuradio/gr/top_block.py", line 103, in start top_block_start_unlocked(self._tb, max_noutput_items) File "/usr/local/lib/python2.7/dist-packages/gnuradio/gr/runtime_swig.py", line 4612, in top_block_start_unlocked return _runtime_swig.top_block_start_unlocked(*args, **kwargs) RuntimeError: pfb_decimator_ccf(13): insufficient connected input ports (5 needed, 1 connected) Does it indicate pfb_decimator_ccf take 5 inputs ? It puzzled me. Best Regards, Jiang Pin