class PointnetSAModuleMSG(_PointnetSAModuleBase): """Pointnet set abstraction layer with multiscale grouping""" def __init__(self, *, npoint: int, radii: List[float], nsamples: List[int], mlps: List[List[int]], bn: bool = True, use_xyz: bool = True, pool_method='max_pool', instance_norm=False): """ :param npoint: int :param radii: list of float, list of radii to group with :param nsamples: list of int, number of samples in each ball query :param mlps: list of list of int, spec of the pointnet before the global pooling for each scale :param bn: whether to use batchnorm :param use_xyz: :param pool_method: max_pool / avg_pool :param instance_norm: whether to use instance_norm """ super().__init__() assert len(radii) == len(nsamples) == len(mlps) self.npoint = npoint self.groupers = nn.ModuleList() self.mlps = nn.ModuleList() for i in range(len(radii)): radius = radii[i] nsample = nsamples[i] self.groupers.append( pointnet2_utils.QueryAndGroup(radius, nsample, use_xyz=use_xyz) if npoint is not None else pointnet2_utils.GroupAll(use_xyz) ) mlp_spec = mlps[i] if use_xyz: mlp_spec[0] += 3 self.mlps.append(pt_utils.SharedMLP(mlp_spec, bn=bn, instance_norm=instance_norm)) self.pool_method = pool_method根据以上代码，我在每一层以上模块的后面都加入了一层注意力机制层，而注意力机制层需要接收该模块的输出，所以该模块的输出是什么呢？

该模块的输出是一个元组，包含了经过多尺度分组后的点集特征向量和对应的索引值。具体来说，输出的第一个元素是一个形状为 (B, C, npoint) 的张量，表示经过多尺度分组后每个点集的特征向量，其中 B 表示 batch size，C 表示特征向量的维度，npoint 表示每个点集的点的数量。输出的第二个元素是一个形状为 (B, npoint, nsample) 的整数张量，表示每个点集中每个点对应的 nsample 个邻域点的索引值。

相关问题

class PointnetSAModuleMSG(_PointnetSAModuleBase):

这是一个 Python 类，它继承自另一个类 PointnetSAModuleBase。它的名称中的 "SA" 是 "Set Abstraction" 的缩写，意思是将一组点分成不同的集合，并对每个集合执行一些操作。"MSG" 则是 "Multi-Scale Grouping" 的缩写，意思是使用多尺度分组来处理每个集合。因此，这个类是一个用于点云数据处理的模块，可以用于分类、分割等任务。

class PointnetSAModuleMSG(_PointnetSAModuleBase): """Pointnet set abstraction layer with multiscale grouping""" def __init__(self, *, npoint: int, radii: List[float], nsamples: List[int], mlps: List[List[int]], bn: bool = True, use_xyz: bool = True, pool_method='max_pool', instance_norm=False): """ :param npoint: int :param radii: list of float, list of radii to group with :param nsamples: list of int, number of samples in each ball query :param mlps: list of list of int, spec of the pointnet before the global pooling for each scale :param bn: whether to use batchnorm :param use_xyz: :param pool_method: max_pool / avg_pool :param instance_norm: whether to use instance_norm """ super().__init__() assert len(radii) == len(nsamples) == len(mlps) self.npoint = npoint self.groupers = nn.ModuleList() self.mlps = nn.ModuleList() for i in range(len(radii)): radius = radii[i] nsample = nsamples[i] self.groupers.append( pointnet2_utils.QueryAndGroup(radius, nsample, use_xyz=use_xyz) if npoint is not None else pointnet2_utils.GroupAll(use_xyz) ) mlp_spec = mlps[i] if use_xyz: mlp_spec[0] += 3 self.mlps.append(pt_utils.SharedMLP(mlp_spec, bn=bn, instance_norm=instance_norm)) self.pool_method = pool_method我想将以上模块输出的张量的shape在模块尾部打印出来方便检查，你可以提供详细的代码吗？

当模块输出的张量维度较多时，可以使用 `torch.Size` 或者 `tuple` 将它们打印出来。以下是添加打印输出的代码示例：

class PointnetSAModuleMSG(_PointnetSAModuleBase):
    """Pointnet set abstraction layer with multiscale grouping"""

    def __init__(
        self,
        *,
        npoint: int,
        radii: List[float],
        nsamples: List[int],
        mlps: List[List[int]],
        bn: bool = True,
        use_xyz: bool = True,
        pool_method='max_pool',
        instance_norm=False
    ):
        """
        :param npoint: int
        :param radii: list of float, list of radii to group with
        :param nsamples: list of int, number of samples in each ball query
        :param mlps: list of list of int, spec of the pointnet before the global pooling for each scale
        :param bn: whether to use batchnorm
        :param use_xyz:
        :param pool_method: max_pool / avg_pool
        :param instance_norm: whether to use instance_norm
        """
        super().__init__()

        assert len(radii) == len(nsamples) == len(mlps)

        self.npoint = npoint
        self.groupers = nn.ModuleList()
        self.mlps = nn.ModuleList()

        for i in range(len(radii)):
            radius = radii[i]
            nsample = nsamples[i]
            self.groupers.append(
                pointnet2_utils.QueryAndGroup(radius, nsample, use_xyz=use_xyz)
                if npoint is not None else pointnet2_utils.GroupAll(use_xyz)
            )
            mlp_spec = mlps[i]
            if use_xyz:
                mlp_spec[0] += 3
            self.mlps.append(pt_utils.SharedMLP(mlp_spec, bn=bn, instance_norm=instance_norm))

        self.pool_method = pool_method

    def forward(self, xyz, features=None):
        """
        :param xyz: (batch_size, num_points, 3) tensor
        :param features: (batch_size, num_points, dim) tensor, optional
        :return:
            new_xyz: (batch_size, npoint, 3) tensor
            new_features: (batch_size, npoint, \sum_k(mlps[k][-1])) tensor
        """
        B, N, C = xyz.shape

        if self.npoint is not None:
            fps_idx = pointnet2_utils.furthest_point_sample(xyz, self.npoint)
            new_xyz = pointnet2_utils.gather_operation(xyz.transpose(1, 2).contiguous(), fps_idx).transpose(1, 2).contiguous()
        else:
            new_xyz = None

        new_features_list = []
        for i, grouper in enumerate(self.groupers):
            grouped_xyz, grouped_features, idx = grouper(new_xyz, xyz, features)

            new_features = self.mlps[i](grouped_features)

            if self.pool_method == 'max_pool':
                new_features = F.max_pool1d(new_features, new_features.size(2)).squeeze(2)  # (B, C, N) -> (B, C)
            elif self.pool_method == 'avg_pool':
                new_features = F.avg_pool1d(new_features, new_features.size(2)).squeeze(2)  # (B, C, N) -> (B, C)

            new_features_list.append(new_features)

        new_features = torch.cat(new_features_list, dim=1)

        # 打印输出张量的形状
        print("new_xyz shape:", new_xyz.shape)
        print("new_features shape:", new_features.shape)

        return new_xyz, new_features

在 `forward` 方法中添加了打印输出，可以直接输出张量的形状信息。