class_docstr: A matrix A\ :subscript:`ij` where i is the row index of the data point and j
  refers to the index of the neigbouring point.
class_docstr_tok: ["A","matrix","A\\",":","subscript",":","`","ij","`","where","i","is","the","row","index","of","the","data","point","and","j","refers","to","the","index","of","the","neigbouring","point","."]
docstr: The width of the matrix (number of neighbours retrieved)
docstr_tok: ["The","width","of","the","matrix","(","number","of","neighbours","retrieved",")"]
code: def k(self):
      """The width of the matrix (number of neighbours retrieved)"""
      raise NotImplementedError
  
imports: from concurrent.futures import ThreadPoolExecutor
  import os
  import shutil
  import time
  from abc import abstractmethod
  from threading import Thread
  from collections.abc import Sequence
  from pathlib import Path
  from scipy.sparse import issparse
  from annoy import AnnoyIndex
  from tqdm import tqdm
  import numpy
  from ..data import get_uint_ctype
label_desc: Use image node_id 1 for calling the NeighbourMatrix obj's underlying member method code with example usage: obj.k() without return types