Returns the selected lines boundaries (start line, end line)

        :return: tuple(int, int)

def selection_range(self):
        """
        Returns the selected lines boundaries (start line, end line)

        :return: tuple(int, int)
        """
        editor = self._editor
        doc = editor.document()
        start = doc.findBlock(
            editor.textCursor().selectionStart()).blockNumber()
        end = doc.findBlock(
            editor.textCursor().selectionEnd()).blockNumber()
        text_cursor = QTextCursor(editor.textCursor())
        text_cursor.setPosition(editor.textCursor().selectionEnd())
        if text_cursor.columnNumber() == 0 and start != end:
            end -= 1
        return start, end