code: def decompile(self):
      (dataLen,) = struct.unpack(">L", self.data[:4])
      data = self.data[4:]
  
      assert dataLen <= len(data), "Data overun in format 19"
      self.imageData = data[:dataLen]
  
imports: from fontTools.misc.textTools import bytesjoin
  from fontTools.misc import sstruct
  from .None import E_B_D_T_
  from .BitmapGlyphMetrics import BigGlyphMetrics, bigGlyphMetricsFormat, SmallGlyphMetrics, smallGlyphMetricsFormat
  from .E_B_D_T_ import BitmapGlyph, BitmapPlusSmallMetricsMixin, BitmapPlusBigMetricsMixin
  import struct
label_desc: Use image node_id 1 for calling the cbdt_bitmap_format_19 obj's underlying member method code with example usage: obj.decompile() without return types