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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 cursors(self):
 """Cursors for rectangular selection. 1 cursor for every line """

        cursors = []
        if self._start is not None:
            startLine, startVisibleCol = self._start
            currentLine, currentCol = self._qpart.cursorPosition
            if abs(startLine - currentLine) > self._MAX_SIZE or \
               abs(startVisibleCol - currentCol) > self._MAX_SIZE:
                # Too big rectangular selection freezes the GUI
                self._qpart.userWarning.emit('Rectangular selection area is too big')
                self._start = None
                return []

            currentBlockText = self._qpart.textCursor().block().text()
            currentVisibleCol = self._realToVisibleColumn(currentBlockText, currentCol)

            for lineNumber in range(min(startLine, currentLine),
                                    max(startLine, currentLine) + 1):
                block = self._qpart.document().findBlockByNumber(lineNumber)
                cursor = QTextCursor(block)
                realStartCol = self._visibleToRealColumn(block.text(), startVisibleCol)
                realCurrentCol = self._visibleToRealColumn(block.text(), currentVisibleCol)
                if realStartCol is None:
                    realStartCol = block.length()  # out of range value
                if realCurrentCol is None:
                    realCurrentCol = block.length()  # out of range value

                cursor.setPosition(cursor.block().position() + min(realStartCol, block.length() - 1))
                cursor.setPosition(cursor.block().position() + min(realCurrentCol, block.length() - 1),
                                   QTextCursor.KeepAnchor)
                cursors.append(cursor)

        return cursors