function contains(pt, arg, pointNumber, searchInfo) {
        var contained = false;
        for(var i = 0; i < testers.length; i++) {
            if(testers[i].contains(pt, arg, pointNumber, searchInfo)) {
                // if contained by subtract tester - exclude the point
                contained = !testers[i].subtract;
            }
        }

        return contained;
    }
Tests if the given point is within this tester.

@param {Array} pt - [0] is the x coordinate, [1] is the y coordinate of the point.
@param {*} arg - An optional parameter to pass down to wrapped testers.
@param {number} pointNumber - The point number of the point within the underlying data array.
@param {number} searchInfo - An object identifying the trace the point is contained in.

@return {boolean} true if point is considered to be selected, false otherwise.