code: def synthesis(self, x):
      x = F.conv_transpose1d(
          x, self.updown_filter * self.N, stride=self.N
      )
      x = F.conv1d(x, self.G, padding=self.taps // 2)
      return x
  
file_path: TTS/TTS/vocoder/layers/pqmf.py
imports: import numpy
  import torch
  import torch.nn.functional
  from scipy import signal
label_desc: Use image node_id 4 for calling the PQMF obj's underlying member method code with example usage: obj.synthesis(x) and returns: x