code: def forward(self, x, return_f=False):
      x = self.conv1(x)
      x = self.conv_bn1(x)
      x = self.conv2(x)
      x = self.conv_bn2(x)
      if return_f is True:
          f = x
      x = self.conv3(x)
      x = F.sigmoid(x)
      if return_f is True:
          return x, f
      return x
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import math
  import paddle
  from paddle import nn
  import paddle.nn.functional
  from paddle import ParamAttr
  from ppocr.modeling.backbones.det_mobilenet_v3 import ConvBNLayer
label_desc: Use image node_id 2 for calling the Head obj's underlying member method code with example usage: obj.forward(x, return_f) and returns: x, x,  f