def add_namespace(self, prefix: str, uri: str) -> Namespace:
        """ Adds a prefix to uri mapping (namespace)

        Adds a namespace to replace any uris in iris with shortened prefixes
        in order to make the file more readable. Not techniqually necessary.

        Args:
            prefix: prefix that will substitute the uri in the iri
            uri: the uri in the iri to be substituted by the prefix

        Returns:
            A namespace of the uri

        Example:
            add_namespace(
                prefix = "rdfs",
                uri = 'http://www.w3.org/2000/01/rdf-schema#',
            )
            makes
            "http://www.w3.org/2000/01/rdf-schema#label 'neuron'@en ;",
            become
            "rdfs:label 'neuron'@en ;"
        """
        ns = Namespace(uri)
        if not self.namespaces.get(prefix):
            self.namespaces[prefix] = ns
            self.g.bind(prefix, uri)
        return ns