Creates a temporary dir (self.temp_dir) and saves the given input
		stream to a file within that dir. Returns the path to the file. The dir
		is removed in the __del__ method.

def _save_stdin(self, stdin):
		"""
		Creates a temporary dir (self.temp_dir) and saves the given input
		stream to a file within that dir. Returns the path to the file. The dir
		is removed in the __del__ method.
		"""
		self.temp_dir = TemporaryDirectory()
		file_path = os.path.join(self.temp_dir.name, 'dataset')

		try:
			with open(file_path, 'w') as f:
				for line in stdin:
					f.write(line)
		except TypeError:
			self.temp_dir.cleanup()
			raise ValueError('Could not read stdin')

		return file_path