code: def _open(self) -> None:
      # The Sun Raster file header is 32 bytes in length
      # and has the following format:
  
      #     typedef struct _SunRaster
      #     {
      #         DWORD MagicNumber;      /* Magic (identification) number */
      #         DWORD Width;            /* Width of image in pixels */
      #         DWORD Height;           /* Height of image in pixels */
      #         DWORD Depth;            /* Number of bits per pixel */
      #         DWORD Length;           /* Size of image data in bytes */
      #         DWORD Type;             /* Type of raster file */
      #         DWORD ColorMapType;     /* Type of color map */
      #         DWORD ColorMapLength;   /* Size of the color map in bytes */
      #     } SUNRASTER;
  
      assert self.fp is not None
  
      # HEAD
      s = self.fp.read(32)
      if not _accept(s):
          msg = "not an SUN raster file"
          raise SyntaxError(msg)
  
      offset = 32
  
      self._size = i32(s, 4), i32(s, 8)
  
      depth = i32(s, 12)
      # data_length = i32(s, 16)   # unreliable, ignore.
      file_type = i32(s, 20)
      palette_type = i32(s, 24)  # 0: None, 1: RGB, 2: Raw/arbitrary
      palette_length = i32(s, 28)
  
      if depth == 1:
          self._mode, rawmode = "1", "1;I"
      elif depth == 4:
          self._mode, rawmode = "L", "L;4"
      elif depth == 8:
          self._mode = rawmode = "L"
      elif depth == 24:
          if file_type == 3:
              self._mode, rawmode = "RGB", "RGB"
          else:
              self._mode, rawmode = "RGB", "BGR"
      elif depth == 32:
          if file_type == 3:
              self._mode, rawmode = "RGB", "RGBX"
          else:
              self._mode, rawmode = "RGB", "BGRX"
      else:
          msg = "Unsupported Mode/Bit Depth"
          raise SyntaxError(msg)
  
      if palette_length:
          if palette_length > 1024:
              msg = "Unsupported Color Palette Length"
              raise SyntaxError(msg)
  
          if palette_type != 1:
              msg = "Unsupported Palette Type"
              raise SyntaxError(msg)
  
          offset = offset + palette_length
          self.palette = ImagePalette.raw(
              "RGB;L", self.fp.read(palette_length)
          )
          if self.mode == "L":
              self._mode = "P"
              rawmode = rawmode.replace("L", "P")
  
      # 16 bit boundaries on stride
      stride = ((self.size[0] * depth + 15) // 16) * 2
  
      # file type: Type is the version (or flavor) of the bitmap
      # file. The following values are typically found in the Type
      # field:
      # 0000h Old
      # 0001h Standard
      # 0002h Byte-encoded
      # 0003h RGB format
      # 0004h TIFF format
      # 0005h IFF format
      # FFFFh Experimental
  
      # Old and standard are the same, except for the length tag.
      # byte-encoded is run-length-encoded
      # RGB looks similar to standard, but RGB byte order
      # TIFF and IFF mean that they were converted from T/IFF
      # Experimental means that it's something else.
      # (https://www.fileformat.info/format/sunraster/egff.htm)
  
      if file_type in (0, 1, 3, 4, 5):
          self.tile = [
              ("raw", (0, 0) + self.size, offset, (rawmode, stride))
          ]
      elif file_type == 2:
          self.tile = [("sun_rle", (0, 0) + self.size, offset, rawmode)]
      else:
          msg = "Unsupported Sun Raster file type"
          raise SyntaxError(msg)
  
imports: from __future__ import annotations
  from .None import Image, ImageFile, ImagePalette
  from ._binary import i32be
label_desc: Use image node_id 1 for calling the SunImageFile obj's underlying member method code with example usage: obj._open() without return types