code: def encode(self, x):
      h = self.encoder(x)
      moments = self.quant_conv(h)
      posterior = DiagonalGaussianDistribution(moments)
      return posterior
  
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 2 for calling the AutoencoderKL obj's underlying member method code with example usage: obj.encode(x) and returns: posterior