class_docstr: A basic class for under-sampling mask setup. It provides common
  features for under-sampling mask generators.
  For example, RandomMaskFunc and EquispacedMaskFunc (two mask
  transform objects defined right after this module)
  both inherit MaskFunc to properly setup properties like the
  acceleration factor.
docstr: This is an extra instance to allow for defining new mask generators.
  For creating other mask transforms, define a new class and simply
  override __call__. See an example of this in
  :py:class:`monai.apps.reconstruction.transforms.array.RandomKspacemask`.
  
  Args:
      kspace: The input k-space data. The shape is (...,num_coils,H,W,2)
          for complex 2D inputs and (...,num_coils,H,W,D) for real 3D
          data.
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code: def __call__(self, kspace: NdarrayOrTensor) -> Sequence[Tensor]:
      """
      This is an extra instance to allow for defining new mask generators.
      For creating other mask transforms, define a new class and simply
      override __call__. See an example of this in
      :py:class:`monai.apps.reconstruction.transforms.array.RandomKspacemask`.
  
      Args:
          kspace: The input k-space data. The shape is (...,num_coils,H,W,2)
              for complex 2D inputs and (...,num_coils,H,W,D) for real 3D
              data.
      """
      raise NotImplementedError
  
imports: from __future__ import annotations
  from abc import abstractmethod
  from collections.abc import Sequence
  import numpy
  from torch import Tensor
  from monai.apps.reconstruction.complex_utils import complex_abs, convert_to_tensor_complex
  from monai.apps.reconstruction.mri_utils import root_sum_of_squares
  from monai.config.type_definitions import NdarrayOrTensor
  from monai.data.fft_utils import ifftn_centered
  from monai.transforms.transform import RandomizableTransform
  from monai.utils.enums import TransformBackends
  from monai.utils.type_conversion import convert_to_tensor
label_desc: Use image node_id 2 for calling the KspaceMask obj's underlying member method code with example usage: obj.__call__(kspace) without return types