code: def set_digit_raw(self, pos, bitmask):
          
          if pos < 0 or pos > 3:
              # Ignore out of bounds digits.
              return
          # Jump past the colon at position 2 by adding a conditional offset.
          offset = 0 if pos < 2 else 1
  
          # Calculate the correct position depending on orientation
          if self.invert:
              pos = 4-(pos+offset)
          else:
              pos = pos+offset
  
          # Set the digit bitmask value at the appropriate position.
          self.buffer[pos*2] = bitmask & 0xFF
docs: Set digit at position to raw bitmask value.  Position should be a value
          of 0 to 3 with 0 being the left most digit on the display.