Opens a file dialog to get the path to a file and put tha tpath in the correct textbox

def open_file_dialog(self):
        """
        Opens a file dialog to get the path to a file and put tha tpath in the correct textbox
        """
        dialog = QtWidgets.QFileDialog
        sender = self.sender()
        if sender == self.btn_open_source:
            textbox = self.source_path
        elif sender == self.btn_open_target:
            textbox = self.target_path
        folder = dialog.getExistingDirectory(self, 'Select a file:', textbox.text(), options = QtWidgets.QFileDialog.ShowDirsOnly)
        if str(folder) != '':
            textbox.setText(folder)
            # load elements from file and display in tree
            if sender == self.btn_open_source:
                self.reset_avaliable(folder)