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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 dim(self, dim):
 """Adjusts contrast to dim the display if dim is True, otherwise sets the contrast to normal brightness if dim is False. """

        # Assume dim display.
        contrast = 0
        # Adjust contrast based on VCC if not dimming.
        if not dim:
            if self._vccstate == SSD1306_EXTERNALVCC:
                contrast = 0x9F
            else:
                contrast = 0xCF