How to use the pandasgui.qtdesigner.scatter.columnPicker function in pandasgui

self.columnDestination.setCurrentItem(self.columnDestination.topLevelItem(0))

        # Add to items to selection section
        self.addTreeItem('test1')
        self.addTreeItem('test2')

    def addTreeItem(self, label):
        # Add to tree
        destinationSection = self.columnDestination.selectedItems()[0]
        treeItem = QtWidgets.QTreeWidgetItem(destinationSection, [label])
        destinationSection.setExpanded(True)
        treeItem.setFlags(treeItem.flags() & ~QtCore.Qt.ItemIsDropEnabled)

import sys
app = QtWidgets.QApplication(sys.argv)
win = columnPicker()
app.exec_()

def initUI(self):
        layout = QtWidgets.QVBoxLayout()
        self.setLayout(layout)
        self.columnPicker = columnPicker()