中文说明：
K近邻算法。是一个理论上比较成熟的方法，也是最简单的机器学习算法之一。该方法的思路是：在特征空间中，如果一个样本附近的k个最近(即特征空间中最邻近)样本的大多数属于某一个类别，则该样本也属于这个类别。
English Description：
K-nearest neighbor algorithm. It is a mature method in theory and one of the simplest machine learning algorithms. The idea of this method is: in the feature space, if most of the k nearest samples near a sample belong to a certain category, then the sample also belongs to this category.