new_contents: #!/usr/bin/env python3
  import sys
  import ast
  
  try:
      file_name, location, new_byte = sys.argv[1:]
  except:
      print("Usage: ./{} file location newbyte".format(sys.argv[0]))
      sys.exit(1)
  
  addr = int(ast.literal_eval(location))
  byte = int(ast.literal_eval(new_byte))
  
  assert 0 <= addr
  assert 0 <= byte < 2**8
  
  with open(file_name, mode="br+") as f:
      f.seek(addr)
      f.write(bytes([byte]))
  
subject: Add new tool to set bytes in file