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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 show_letter( self, s, text_colour=[255, 255, 255], back_colour=[0, 0, 0] ):
 """ Displays a single text character on the LED matrix using the specified colours """


        if len(s) > 1:
            raise ValueError('Only one character may be passed into this method')
        # We must rotate the pixel map left through 90 degrees when drawing
        # text, see _load_text_assets
        previous_rotation = self._rotation
        self._rotation -= 90
        if self._rotation < 0:
            self._rotation = 270
        dummy_colour = [None, None, None]
        pixel_list = [dummy_colour] * 8
        pixel_list.extend(self._get_char_pixels(s))
        pixel_list.extend([dummy_colour] * 16)
        coloured_pixels = [
            text_colour if pixel == [255, 255, 255] else back_colour
            for pixel in pixel_list
        ]
        self.set_pixels(coloured_pixels)
        self._rotation = previous_rotation