def dataset_by_id(self,id):
		Retrieve a specific data set using its agency assigned ID
		if (id is None):
			raise ValueError("You must specify an id")
		request = "/0.4/get_dataset?id_agency=" + id
		js = self.send_request(request)
		dataset = UNDataCatalogDataset()
		attributes = js['dataset']
		for attr in attributes:
			if (attributes[attr]):
		return dataset
	def datasets_by_organization(self,organization,published = None):
		Returns the collection of datasets published by the specified
		organization.  If the boolean parameter published is not specified, 
		then the method will return the published datasets.
		if (organization is None):
			raise ValueError("You must specify an organization")
		if (published not in (None, True, False)):
			raise ValueError("If specified, you must set published to True or False")
		if (published is None):
			published = True;	
		request = ("/0.4/dataset_get_by_organization?organization=" + organization + 
			   "&published=" + ("1" if published else "0") )
		js = self.send_request(request)
		datasets = set()
		for ds in js['datasets']:
			dataset = UNDataCatalogDataset()
			for attr in ds:
				if (ds[attr]):
		return datasets