code: def forward(self, sample, sample_posterior=False):
      x = sample
      posterior = self.encode(x)
      if sample_posterior:
          z = posterior.sample()
      else:
          z = posterior.mode()
      dec = self.decode(z)
      return dec
  
imports: import numpy
  import paddle
  import paddle.nn
  from ..configuration_utils import ConfigMixin
  from ..configuration_utils import register_to_config
  from .unet_blocks import get_down_block
  from .unet_blocks import get_up_block
  from .unet_blocks import UNetMidBlock2D
label_desc: Use image node_id 4 for calling the AutoencoderKL obj's underlying member method code with example usage: obj.forward(sample, sample_posterior) and returns: dec