class_docstr: Retrieves neighbour indices according to class labels provided in constructor.
  Rows with the same label will be regarded as neighbours.
docstr: Retrieves the neighbours for the row index provided
docstr_tok: ["Retrieves","the","neighbours","for","the","row","index","provided"]
code: def __getitem__(self, idx):
      """Retrieves the neighbours for the row index provided"""
      return self.class_indicies[self.labels[idx]]
  
imports: from collections.abc import Sequence
  import numpy
label_desc: Use image node_id 3 for calling the LabeledNeighbourMap obj's underlying member method code with example usage: obj.__getitem__(idx) and returns: self