<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_thresholdcurve_data(data, xname, yname):
 """ Retrieves x and y columns from of the data generated by the weka.classifiers.evaluation.ThresholdCurve class. :param data: the threshold curve data :type data: Instances :param xname: the name of the X column :type xname: str :param yname: the name of the Y column :type yname: str :return: tuple of x and y arrays :rtype: tuple """

    xi = data.attribute_by_name(xname).index
    yi = data.attribute_by_name(yname).index
    x = []
    y = []
    for i in range(data.num_instances):
        inst = data.get_instance(i)
        x.append(inst.get_value(xi))
        y.append(inst.get_value(yi))
    return x, y