[op25-dev] AttributeError: 'module' object has no attribute 'fsk4_slicer_fb'

using the command in terminal: cd ~/src/op25/python ./audio_p25_rx.py -a i get this error: Using Volk machine: ssse3_32 Traceback (most recent call last): File "./audio_p25_rx.py", line 1044, in <module> app = stdgui2.stdapp(p25_rx_block, "APCO P25 Receiver", 3) File "/usr/local/lib/python2.7/dist-packages/gnuradio/wxgui/stdgui2.py", line 38, in __init__ wx.App.__init__ (self, redirect=False) File "/usr/lib/python2.7/dist-packages/wx-2.8-gtk2-unicode/wx/_core.py", line 7981, in __init__ self._BootstrapApp() File "/usr/lib/python2.7/dist-packages/wx-2.8-gtk2-unicode/wx/_core.py", line 7555, in _BootstrapApp return _core_.PyApp__BootstrapApp(*args, **kwargs) File "/usr/local/lib/python2.7/dist-packages/gnuradio/wxgui/stdgui2.py", line 42, in OnInit self._max_noutput_items) File "/usr/local/lib/python2.7/dist-packages/gnuradio/wxgui/stdgui2.py", line 64, in __init__ self.panel = stdpanel (self, self, top_block_maker, max_nouts) File "/usr/local/lib/python2.7/dist-packages/gnuradio/wxgui/stdgui2.py", line 86, in __init__ self.top_block = top_block_maker (frame, self, vbox, sys.argv) File "./audio_p25_rx.py", line 97, in __init__ self.__init_gui(frame, panel, vbox) File "./audio_p25_rx.py", line 298, in __init_gui self.slicer = op25.fsk4_slicer_fb(levels) AttributeError: 'module' object has no attribute 'fsk4_slicer_fb' can anybody help me with this error please?