docs: def IsBinary(self, filename):
  		"""Returns true if the guessed mimetyped isnt't in text group."""
  		mimetype = mimetypes.guess_type(filename)[0]
  		if not mimetype:
  			return False  # e.g. README, "real" binaries usually have an extension
  		# special case for text files which don't start with text/
  		if mimetype in TEXT_MIMETYPES:
  			return False
  		return not mimetype.startswith("text/")