class_docstr: get dataset from
  https://github.com/stanis-morozov/ip-nsw#dataset
class_docstr_tok: ["get","dataset","from","https",":","\/\/github.com\/stanis-morozov\/ip-nsw","#","dataset"]
code: def get_groundtruth(self, k=None):
      gt = np.load(self.basedir + "gt.npy")
      if k is not None:
          assert k <= 100
          gt = gt[:, :k]
      return gt
  
imports: import os
  import numpy
  import faiss
  from .vecs_io import fvecs_read, ivecs_read, bvecs_mmap, fvecs_mmap
  from .exhaustive_search import knn
label_desc: Use image node_id 4 for calling the DatasetMusic100 obj's underlying member method code with example usage: obj.get_groundtruth(k) and returns: gt