Return value with given key or index.

		If no value is found, return d (None by default).

def get(self, key=NOT_SET, index=NOT_SET, d=None):
		"""Return value with given key or index.

		If no value is found, return d (None by default).
		"""
		if index is NOT_SET and key is not NOT_SET:
			try:
				index, value = self._dict[key]
			except KeyError:
				return d
			else:
				return value
		elif index is not NOT_SET and key is NOT_SET:
			try:
				key, value = self._list[index]
			except IndexError:
				return d
			else:
				return value
		else:
			raise KEY_EQ_INDEX_ERROR