class_docstr: Args:
      ch_in (int): The channel number of input Tensor.
      ch_out (int): The channel number of output Tensor.
      num_classes (int): Number of classes.
      conv_num (int): The convolution number of hm_feat.
      dcn_head(bool): whether use dcn in head. False by default. 
      lite_head(bool): whether use lite version. False by default.
      norm_type (string): norm type, 'sync_bn', 'bn', 'gn' are optional.
          bn by default
  
  Return:
      Heatmap head output
code: def forward(self, feat):
      out = self.feat(feat)
      out = self.head(out)
      return out
  
imports: import paddle
  import paddle.nn
  import paddle.nn.functional
  from paddle import ParamAttr
  from paddle.nn.initializer import Constant, Normal
  from paddle.regularizer import L2Decay
  from ppdet.core.workspace import register
  from ppdet.modeling.layers import DeformableConvV2, LiteConv
  import numpy
label_desc: Use image node_id 2 for calling the HMHead obj's underlying member method code with example usage: obj.forward(feat) and returns: out