code: def test_one_label_at_100(self):
      y_true = np.array(
          [1, nan, nan, nan, nan, nan, 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=1.0, normalize=False
      )
      self.assertEqual(labels, 1)
  
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 7 for calling the Test_labels_at obj's underlying member method code with example usage: obj.test_one_label_at_100() without return types