code: def merge_specific_instructions(chunks, join_preamble=True, join_raster=True):
      
      new_instructions = []
      last_opcode = None
      instruction_buffer = b''
      for instruction in chunks:
          opcode = match_opcode(instruction)
          if   join_preamble and OPCODES[opcode][0] == 'preamble' and last_opcode == 'preamble':
              instruction_buffer += instruction
          elif join_raster   and 'raster' in OPCODES[opcode][0] and 'raster' in last_opcode:
              instruction_buffer += instruction
          else:
              if instruction_buffer:
                  new_instructions.append(instruction_buffer)
              instruction_buffer = instruction
          last_opcode = OPCODES[opcode][0]
      if instruction_buffer:
          new_instructions.append(instruction_buffer)
      return new_instructions
docs: Process a list of instructions by merging subsequent instuctions with
      identical opcodes into "large instructions".