def init_vision_encoder_umt(self, config):
        """build vision encoder
        Returns: (vision_encoder, vision_layernorm). Each is a `nn.Module`.

        """
        vision_encoder = build_vit(config)

        if config.vision_encoder.vit_add_ln:
            vision_layernorm = nn.LayerNorm(config.vision_encoder.encoder_embed_dim, eps=1e-12)
        else:
            vision_layernorm = nn.Identity()

        return vision_encoder, vision_layernorm
build vision encoder
        Returns: (vision_encoder, vision_layernorm). Each is a `nn.Module`.

        
video_chat2/models/blip2/blip2.py