docstr: Check and initialize input transforms.
          
docstr_tok: ["Check","and","initialize","input","transforms","."]
code: def _init_inputs(self, in_channels, in_index, input_transform):
      """Check and initialize input transforms."""
  
      if input_transform is not None:
          assert input_transform in ["resize_concat", "multiple_select"]
      self.input_transform = input_transform
      self.in_index = in_index
      if input_transform is not None:
          assert isinstance(in_channels, (list, tuple))
          assert isinstance(in_index, (list, tuple))
          assert len(in_channels) == len(in_index)
          if input_transform == "resize_concat":
              self.in_channels = sum(in_channels)
          else:
              self.in_channels = in_channels
      else:
          assert isinstance(in_channels, int)
          assert isinstance(in_index, int)
          self.in_channels = in_channels
  
file_path: PaddleDetection/ppdet/modeling/heads/vitpose_head.py
imports: import paddle
  import paddle.nn
  import paddle.nn.functional
  from ppdet.core.workspace import register
  from ppdet.modeling.keypoint_utils import resize, flip_back
  from paddle.nn.initializer import TruncatedNormal, Constant, Normal
  from ppdet.modeling.layers import ConvTranspose2d, BatchNorm2d
label_desc: Use image node_id 3 for calling the TopdownHeatmapSimpleHead obj's underlying member method code with example usage: obj._init_inputs(in_channels, in_index, input_transform) without return types