Parent `Compose`'s `map_items` is passed down to a child `Compose` even though it specifies its own

[ibro45]

Is your feature request related to a problem? Please describe.
I tried defining a Compose within a Compose with a different map_items argument, but the one from the parent Compose doesn't get overridden.

Only once I defined the parent Compose to be a torchvision one instead of monai, it worked, as the torchvision one doesn't have a map_items argument to pass down.

Describe the solution you'd like
A nested Compose should override the parent Compose's arguments.

Describe alternatives you've considered

Additional context

Monai Bundle Config style example of what I'm doing. In this example, I need to wrap the final list into a dict to indicate that it's an input only, and not an input and target.

system#datasets#train#transform:
    # Parent torchvision Compose so that the monai Compose children can have different map_items.
    # A parent monai Compose would force all children to have its map_items.
    _target_: torchvision.transforms.Compose
    transforms:
        - _target_: monai.transforms.Compose
          # `map_items=True` - When input to a Transform is a list, apply the transform to each element of the list.
          map_items: True
          transforms:
              - _target_: monai.transforms.LoadImage
                image_only: True
              - _target_: monai.transforms.EnsureChannelFirst
              - _target_: monai.transforms.Orientation
                axcodes: SPL
                lazy: True
              - _target_: monai.transforms.Spacing
                pixdim: "%CONSTANTS#SPACING"
                mode: bilinear
                lazy: True
              - _target_: monai.transforms.CropForeground
                lazy: True
              - _target_: monai.transforms.SpatialPad
                spatial_size: "%CONSTANTS#PATCH_SIZE_VOXELS"
                value: -1024
                lazy: True
              - _target_: monai.transforms.ScaleIntensityRange
                a_min: -1024
                a_max: 2048
                b_min: 0
                b_max: 1
                clip: True
              # Turn into a dict of views
              - _target_: monai.transforms.Lambda
                func: '$lambda x: {"view_0": x}'
              # From this point it's not a Tensor anymore, but a list of NUM_CONTRASTIVE_CROPS Tensors
              - _target_: monai.transforms.RandSpatialCropSamplesd
                keys: view_0
                roi_size: "%CONSTANTS#PATCH_SIZE_VOXELS"
                num_samples: "%CONSTANTS#NUM_CONTRASTIVE_CROPS"
                lazy: True
              # Duplicate the view
              - _target_: monai.transforms.CopyItemsd
                keys: view_0
                names: view_1
              - _target_: project.transforms.ssl.DictifyTransform
                keys: view_0
                transform:
                    _target_: project.transforms.ssl.RandomResizedCrop
                    size: "%CONSTANTS#PATCH_SIZE_VOXELS"
                    scale: [0.33, 1.0]
              - _target_: project.transforms.ssl.DictifyTransform
                keys: view_1
                transform:
                    _target_: project.transforms.ssl.RandomResizedCrop
                    size: "%CONSTANTS#PATCH_SIZE_VOXELS"
                    scale: [0.33, 1.0]
              - _target_: monai.transforms.RandFlipd
                keys: view_0
                spatial_axis: [0]
                prob: 0.5
                lazy: True
              - _target_: monai.transforms.RandFlipd
                keys: view_1
                spatial_axis: [0]
                prob: 0.5
                lazy: True
              - _target_: monai.transforms.RandHistogramShiftd
                keys: view_0
                prob: 0.5
                num_control_points: 5  # Makes distortion stronger
              - _target_: monai.transforms.RandHistogramShiftd
                keys: view_1
                prob: 0.5
                num_control_points: 5  # Makes distortion stronger
              - _target_: monai.transforms.RandGaussianSmoothd
                keys: view_0
                prob: 0.5
              - _target_: monai.transforms.RandGaussianSmoothd
                keys: view_1
                prob: 0.5
              - _target_: monai.transforms.ToTensord
                keys: ["view_0", "view_1"]
                track_meta: False
              - _target_: monai.transforms.Lambda
                func: '$lambda x: (x["view_0"], x["view_1"])'

        # Disable map_items so that the whole list of NUM_CONTRASTIVE_CROPS Tensors is wrapped into input instead of its elements
        - _target_: monai.transforms.Compose
          map_items: False
          transforms:
              - _target_: monai.transforms.Lambda
                func: '$lambda x: {"input": x}'

[atbenmurray]

@ibro45, @KumoLiu hi folks, let me take a look at this