def add_format(self, mimetype, format, requires_context=False):
		""" Registers a new format to be used in a graph's serialize call
		    If you've installed an rdflib serializer plugin, use this
		    to add it to the content negotiation system
		    Set requires_context=True if this format requires a context-aware graph
		"""
		self.formats[mimetype] = format
		if not requires_context:
			self.ctxless_mimetypes.append(mimetype)
		self.all_mimetypes.append(mimetype)
Registers a new format to be used in a graph's serialize call
		    If you've installed an rdflib serializer plugin, use this
		    to add it to the content negotiation system
		    Set requires_context=True if this format requires a context-aware graph