Overridden :meth:`.WSimplePadding._fill` method. This methods adds padding symbol at the beginning
		and at the end of the specified data.

		:param data: data to append to
		:param total_length: target length
		:param padding_symbol: symbol to pad
		:return: bytes

def _fill(self, data, total_length, padding_symbol):
		""" Overridden :meth:`.WSimplePadding._fill` method. This methods adds padding symbol at the beginning
		and at the end of the specified data.

		:param data: data to append to
		:param total_length: target length
		:param padding_symbol: symbol to pad
		:return: bytes
		"""

		delta = total_length - len(data)
		return ((padding_symbol * random_int(delta)) + data).ljust(total_length, padding_symbol)