for a given prefix:name, return {namespace}name from the given namespaces dict

def prefixed_to_namespaced(C, prefixed_name, namespaces):
        """for a given prefix:name, return {namespace}name from the given namespaces dict
        """
        if ':' not in prefixed_name:
            return prefixed_name
        else:
            prefix, name = prefixed_name.split(':')
            namespace = namespaces[prefix]
            return "{%s}%s" % (namespace, name)