if value is valid sets the data to value
        Args:
            column: column of item
            role: role of item (see Qt doc)
            value: value to be set

def setData(self, column, role, value):
        """
        if value is valid sets the data to value
        Args:
            column: column of item
            role: role of item (see Qt doc)
            value: value to be set
        """
        assert isinstance(column, int)
        assert isinstance(role, int)

        # make sure that the right row is selected, this is not always the case for checkboxes and
        # combo boxes because they are items on top of the tree structure
        if isinstance(value, (QtWidgets.QComboBox, QtWidgets.QCheckBox)):
            self.treeWidget().setCurrentItem(self)

        # if row 2 (editrole, value has been entered)
        if role == 2 and column == 1:

            if isinstance(value, str):
                value = self.cast_type(value) # cast into same type as valid values

            if isinstance(value, QtCore.QVariant):
                value = self.cast_type(value.toString())  # cast into same type as valid values

            if isinstance(value, QtWidgets.QComboBox):
                value = self.cast_type(value.currentText())

            if isinstance(value, QtWidgets.QCheckBox):
                value = bool(int(value.checkState()))  # checkState() gives 2 (True) and 0 (False)

            # save value in internal variable
            self.value = value

        elif column == 0:
            # labels should not be changed so we set it back
            value = self.name

        if value is None:
            value = self.value

        # 180327(asafira) --- why do we need to do the following lines? Why not just always call super or always
        # emitDataChanged()?
        if not isinstance(value, bool):
            super(B26QTreeItem, self).setData(column, role, value)

        else:
            self.emitDataChanged()