class_docstr: This module is used in RetinaNet to generate extra layers, P6 and P7.
  Serves as an ``extra_blocks``
  in :class:`~monai.networks.blocks.feature_pyramid_network.FeaturePyramidNetwork` .
code: def __init__(
      self, spatial_dims: int, in_channels: int, out_channels: int
  ):
      super().__init__()
      conv_type: Callable = Conv[Conv.CONV, spatial_dims]
      self.p6 = conv_type(
          in_channels, out_channels, kernel_size=3, stride=2, padding=1
      )
      self.p7 = conv_type(
          out_channels, out_channels, kernel_size=3, stride=2, padding=1
      )
      for module in [self.p6, self.p7]:
          nn.init.kaiming_uniform_(module.weight, a=1)
          nn.init.constant_(module.bias, 0)
      self.use_P5 = in_channels == out_channels
  
imports: from __future__ import annotations
  from collections import OrderedDict
  from collections.abc import Callable
  import torch.nn.functional
  from torch import Tensor, nn
  from monai.networks.layers.factories import Conv, Pool
label_desc: Use image node_id 1 to create a new LastLevelP6P7 object from inherited base classes: ExtraFPNBlock with example: obj = LastLevelP6P7(spatial_dims, in_channels, out_channels)