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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 _check_one_size(self):
        '''
        Checks for single height or single width blocks and flags the occurrence.

        Returns:
            True if the block is size 1.
        '''
        block_one = self.end[0] == self.start[0]+1 or self.end[1] == self.start[1]+1
        if block_one:
            self.flag_change(self.flags, 'error', self.start, self.worksheet,
                             message=self.FLAGS['1-size'])
        return block_one