code: def forward(self, x):
      x = self.conv(x)
      x = self.bn(x)
      if self.act is not None:
          if self.act == "relu":
              x = F.relu(x)
          elif self.act == "relu6":
              x = F.relu6(x)
          elif self.act == "hard_swish":
              x = F.hardswish(x)
          else:
              raise NotImplementedError(
                  "The activation function is selected incorrectly."
              )
      return x
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import paddle
  import paddle.nn
  import paddle.nn.functional
  from paddle import ParamAttr
  from paddle.regularizer import L2Decay
  from ppdet.core.workspace import register, serializable
  from numbers import Integral
  from ..shape_spec import ShapeSpec
label_desc: Use image node_id 2 for calling the ConvBNLayer obj's underlying member method code with example usage: obj.forward(x) and returns: x