code: def test_60_labels_at_60_norm(self):
      y_true = np.array([1, 1, 1, 1, 1, 1, nan, nan, nan, nan])
      y_score = np.array(
          [1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1]
      )
      labels = labels_at(
          y_true, y_score, top_proportion=0.6, normalize=True
      )
      self.assertEqual(labels, 1.0)
  
imports: from unittest import TestCase
  from sklearn_evaluation.metrics import precision_at, labels_at, tp_at, fp_at
  import numpy
  from numpy import nan
label_desc: Use image node_id 9 for calling the Test_labels_at obj's underlying member method code with example usage: obj.test_60_labels_at_60_norm() without return types