Creates single training example.
    :param candidate_dialog_paths:
    :param rng:
    :param positive_probability: probability of selecting positive training example
    :return:

def create_examples_train(candidate_dialog_paths, rng, positive_probability=0.5, max_context_length=20):
    """
    Creates single training example.
    :param candidate_dialog_paths:
    :param rng:
    :param positive_probability: probability of selecting positive training example
    :return:
    """
    i = 0
    examples = []
    for context_dialog in candidate_dialog_paths:
        if i % 1000 == 0:
            print str(i)
        dialog_path = candidate_dialog_paths[i]
        examples.append(create_single_dialog_train_example(dialog_path, candidate_dialog_paths, rng, positive_probability,
                                                           max_context_length=max_context_length))
        i += 1