class_docstr: The ViT-Adapter
      
code: def _add_level_embed(self, c2, c3, c4):
      c2 = c2 + self.level_embed[0]
      c3 = c3 + self.level_embed[1]
      c4 = c4 + self.level_embed[2]
      return c2, c3, c4
  
imports: import math
  from functools import partial
  import numpy
  import paddle
  import paddle.nn
  import paddle.nn.functional
  from paddleseg.cvlibs import manager
  from paddleseg.utils import utils, logger
  from paddleseg.cvlibs.param_init import normal_init, trunc_normal_init, constant_init
  from paddleseg.models.backbones.transformer_utils import to_2tuple, DropPath
  from paddleseg.models.layers.vit_adapter_layers import SpatialPriorModule, InteractionBlock, deform_inputs
  from paddleseg.models.layers.ms_deformable_attention import MSDeformAttn
label_desc: Use image node_id 5 for calling the ViTAdapter obj's underlying member method code with example usage: obj._add_level_embed(c2, c3, c4) and returns: c2,  c3,  c4