def METHOD_NAME(X_inliers, X_outliers, inlier_color='blue',
          outlier_color='orange'):
    """Internal method to add subplot of inliers and outliers.
    Parameters
    ----------
    X_inliers : numpy array of shape (n_samples, n_features)
        Outliers.
    X_outliers : numpy array of shape (n_samples, n_features)
        Inliers.
    sub_plot_title : str
        Subplot title.
    inlier_color : str, optional (default='blue')
        The color of inliers.
    outlier_color : str, optional (default='orange')
        The color of outliers.
    """
    plt.axis("equal")
    plt.scatter(X_inliers[:, 0], X_inliers[:, 1], label='inliers',
                color=inlier_color, s=40)
    plt.scatter(X_outliers[:, 0], X_outliers[:, 1],
                label='outliers', color=outlier_color, s=50, marker='^')
    plt.xticks([])
    plt.yticks([])
    plt.legend(loc='best', prop={'size': 10})