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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 __move_line_or_selection(self, after_current_line=True):

 """Move current line or selected text"""

        cursor = self.textCursor()
        cursor.beginEditBlock()
        start_pos, end_pos = self.__save_selection()
        last_line = False

        # ------ Select text

        # Get selection start location
        cursor.setPosition(start_pos)
        cursor.movePosition(QTextCursor.StartOfBlock)
        start_pos = cursor.position()

        # Get selection end location
        cursor.setPosition(end_pos)
        if not cursor.atBlockStart() or end_pos == start_pos:
            cursor.movePosition(QTextCursor.EndOfBlock)
            cursor.movePosition(QTextCursor.NextBlock)
        end_pos = cursor.position()

        # Check if selection ends on the last line of the document
        if cursor.atEnd():
            if not cursor.atBlockStart() or end_pos == start_pos:
                last_line = True

        # ------ Stop if at document boundary

        cursor.setPosition(start_pos)
        if cursor.atStart() and not after_current_line:
            # Stop if selection is already at top of the file while moving up
            cursor.endEditBlock()
            self.setTextCursor(cursor)
            self.__restore_selection(start_pos, end_pos)
            return

        cursor.setPosition(end_pos, QTextCursor.KeepAnchor)
        if last_line and after_current_line:
            # Stop if selection is already at end of the file while moving down
            cursor.endEditBlock()
            self.setTextCursor(cursor)
            self.__restore_selection(start_pos, end_pos)
            return

        # ------ Move text

        sel_text = to_text_string(cursor.selectedText())
        cursor.removeSelectedText()


        if after_current_line:
            # Shift selection down
            text = to_text_string(cursor.block().text())
            sel_text = os.linesep + sel_text[0:-1]  # Move linesep at the start
            cursor.movePosition(QTextCursor.EndOfBlock)
            start_pos += len(text)+1
            end_pos += len(text)
            if not cursor.atEnd():
                end_pos += 1
        else:
            # Shift selection up
            if last_line:
                # Remove the last linesep and add it to the selected text
                cursor.deletePreviousChar()
                sel_text = sel_text + os.linesep
                cursor.movePosition(QTextCursor.StartOfBlock)
                end_pos += 1
            else:
                cursor.movePosition(QTextCursor.PreviousBlock)
            text = to_text_string(cursor.block().text())
            start_pos -= len(text)+1
            end_pos -= len(text)+1

        cursor.insertText(sel_text)

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