class_docstr: CBHG module to convert log Mel-filterbanks to linear spectrogram.
  
  This is a module of CBHG introduced
  in `Tacotron: Towards End-to-End Speech Synthesis`_.
  The CBHG converts the sequence of log Mel-filterbanks into linear spectrogram.
  
  .. _`Tacotron: Towards End-to-End Speech Synthesis`:
       https://arxiv.org/abs/1703.10135
class_docstr_tok: ["CBHG","module","to","convert","log","Mel-filterbanks","to","linear","spectrogram",".","This","is","a","module","of","CBHG","introduced","in","`","Tacotron",":","Towards","End-to-End","Speech","Synthesis","`","_",".","The","CBHG","converts","the","sequence","of","log","Mel-filterbanks","into","linear","spectrogram",".","..","_","`","Tacotron",":","Towards","End-to-End","Speech","Synthesis","`",":","https",":","\/\/arxiv.org\/abs\/1703.10135"]
code: def _sort_by_length(self, xs, ilens):
      sort_ilens, sort_idx = ilens.sort(0, descending=True)
      return xs[sort_idx], ilens[sort_idx], sort_idx
  
file_path: espnet/espnet/nets/pytorch_backend/tacotron2/cbhg.py
imports: import torch
  import torch.nn.functional
  from torch.nn.utils.rnn import pack_padded_sequence, pad_packed_sequence
  from espnet.nets.pytorch_backend.nets_utils import make_non_pad_mask
label_desc: Use image node_id 4 for calling the CBHG obj's underlying member method code with example usage: obj._sort_by_length(xs, ilens) and returns: xs,  ilens,  sort_idx