text: from mmcv.utils import Registry, build_from_cfg
  
  BVR_ATTENTION = Registry('Attention_Layer')
  BVR_POSITIONAL_ENCODING = Registry('Positional_Encoding')
  BVR_TRANSFORMER = Registry('BVR_Transformer')
  
  
  def build_attention_layer(cfg, default_args=None):
      """Builder for Transformer."""
      return build_from_cfg(cfg, BVR_ATTENTION, default_args)
  
  
  def build_positional_encoding(cfg, default_args=None):
      """Builder for Transformer."""
      return build_from_cfg(cfg, BVR_POSITIONAL_ENCODING, default_args)
  
  
  def build_transformer(cfg, default_args=None):
      return build_from_cfg(cfg, BVR_TRANSFORMER, default_args)
  