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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def __duplicate_line_or_selection(self, after_current_line=True):

 """Duplicate current line or selected text"""

        cursor = self.textCursor()
        cursor.beginEditBlock()
        start_pos, end_pos = self.__save_selection()
        if to_text_string(cursor.selectedText()):
            cursor.setPosition(end_pos)
            # Check if end_pos is at the start of a block: if so, starting
            # changes from the previous block
            cursor.movePosition(QTextCursor.StartOfBlock,
                                QTextCursor.KeepAnchor)
            if not to_text_string(cursor.selectedText()):
                cursor.movePosition(QTextCursor.PreviousBlock)
                end_pos = cursor.position()

        cursor.setPosition(start_pos)
        cursor.movePosition(QTextCursor.StartOfBlock)
        while cursor.position() <= end_pos:
            cursor.movePosition(QTextCursor.EndOfBlock, QTextCursor.KeepAnchor)
            if cursor.atEnd():
                cursor_temp = QTextCursor(cursor)
                cursor_temp.clearSelection()
                cursor_temp.insertText(self.get_line_separator())
                break
            cursor.movePosition(QTextCursor.NextBlock, QTextCursor.KeepAnchor)
        text = cursor.selectedText()
        cursor.clearSelection()

        if not after_current_line:
            # Moving cursor before current line/selected text
            cursor.setPosition(start_pos)
            cursor.movePosition(QTextCursor.StartOfBlock)
            start_pos += len(text)
            end_pos += len(text)

        cursor.insertText(text)
        cursor.endEditBlock()
        self.setTextCursor(cursor)
        self.__restore_selection(start_pos, end_pos)