class_docstr: Log STFT magnitude loss.
  
  Args:
      epsilon (float): Epsilon value for numerical stability.
docstr: Calculate forward propagation.
  
  Args:
      x_mag (torch.Tensor): Magnitude spectrogram of predicted signal (B, #frames, #freq_bins).
      y_mag (torch.Tensor): Magnitude spectrogram of groundtruth signal (B, #frames, #freq_bins).
  Returns:
      torch.Tensor: Log STFT magnitude loss value.
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code: def forward(self, x_mag: torch.Tensor, y_mag: torch.Tensor):
      """Calculate forward propagation.
  
      Args:
          x_mag (torch.Tensor): Magnitude spectrogram of predicted signal (B, #frames, #freq_bins).
          y_mag (torch.Tensor): Magnitude spectrogram of groundtruth signal (B, #frames, #freq_bins).
      Returns:
          torch.Tensor: Log STFT magnitude loss value.
      """
      return F.l1_loss(
          torch.log(self.epsilon + y_mag),
          torch.log(self.epsilon + x_mag),
      )
  
imports: import typing
  import torch
  from torch import nn
  from torch.nn import functional
label_desc: Use image node_id 2 for calling the LogSTFTMagnitudeLoss obj's underlying member method code with example usage: obj.forward(x_mag, y_mag) and returns: F