code: def test_cluster_map_clear():
      nb_clusters = 11
      clusters = ClusterMap()
      for i in range(nb_clusters):
          new_cluster = Cluster(indices=range(i))
          clusters.add_cluster(new_cluster)
  
      clusters.clear()
      assert_equal(len(clusters), 0)
      assert_array_equal(list(itertools.chain(*clusters)), [])
  
imports: import copy
  import itertools
  import numpy
  from numpy.testing import assert_array_equal, assert_raises, assert_equal
  from dipy.segment.clustering import Cluster, ClusterCentroid
  from dipy.segment.clustering import ClusterMap, ClusterMapCentroid
  from dipy.segment.clustering import Clustering
  from dipy.testing import assert_true, assert_false, assert_arrays_equal
  from dipy.testing.decorators import set_random_number_generator
label_desc: Use image node_id 13 for calling a global function with example usage: test_cluster_map_clear() without return types