class_docstr: A mask backed by a dense numpy array.
class_docstr_tok: ["A","mask","backed","by","a","dense","numpy","array","."]
code: def __getitem__(self, idx) -> np.ndarray:
      return self.array[idx]
  
imports: from __future__ import annotations
  import dataclasses
  from typing import Any, Callable, Sequence, Tuple
  import numpy
label_desc: Use image node_id 3 for calling the NumpyMask obj's underlying member method code with example usage: obj.__getitem__(idx) and returns: self