Question about the README of PitchDNN model

[YYX666660]

Hi~ :)
I have trouble in training the PitchDNN model. The README of neural-pitch reveals that "To extract xcorr, add lpcnet_extractor.c and add relevant functions to lpcnet_enc.c, add source for headers/c files and Makefile.am, and compile to generate ./lpcnet_xcorr_extractor object".

But I didn't find the lpcnet_extractor.c in the repository, so where can I find this file? Could you please show me the guidance?
@jmvalin