code: def forward(self, x, prev_rgb, istyle):
      style = self.to_style(istyle)
      x = self.conv(x, style)
  
      if prev_rgb is not None:
          x = x + prev_rgb
  
      if self.upsample is not None:
          x = self.upsample(x)
  
      return x
  
imports: import math
  from functools import partial
  from math import log2
  from typing import List
  import torch
  import torch.nn.functional
  from einops import rearrange
  from kornia.filters import filter2d
  from nemo.collections.tts.parts.utils.helpers import mask_sequence_tensor
label_desc: Use image node_id 2 for calling the RGBBlock obj's underlying member method code with example usage: obj.forward(x, prev_rgb, istyle) and returns: x