def add(self, data):
		"""
		>>> ob = OutBuffer().add(OutBuffer.sizelimit * b"x")
		>>> ob.add(b"y") # doctest: +ELLIPSIS
		Traceback (most recent call last):
		...
		OmapiSizeLimitError: ...

		@type data: bytes
		@returns: self
		@raises OmapiSizeLimitError:
		"""
		if len(self) + len(data) > self.sizelimit:
			raise OmapiSizeLimitError()
		self.buff.write(data)
		return self