code: def leave1out(learner, dataset):
      "Leave one out cross-validation over the dataset."
      return cross_validation(learner, dataset, k=len(dataset.examples)f leave1out(learner, dataset):
      "Leave one out cross-validation over the dataset."
      return cross_validation(learner, dataset, k=len(dataset.examples))
docs: Leave one out cross-validation over the dataset.