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/")
Returns true if the guessed mimetyped isnt't in text group.