Set a resource uri for this instance. If no resource exists, create
        a new one with the given protocol info.

        Args:
            uri (str): The resource uri.
            resource_nr (int): The index of the resource on which to set the
                uri. If it does not exist, a new resource is added to the list.
                Note that by default, only the uri of the first resource is
                used for playing the item.
            protocol_info (str): Protocol info for the resource. If none is
                given and the resource does not exist yet, a default protocol
                info is constructed as '[uri prefix]:*:*:*'.

def set_uri(self, uri, resource_nr=0, protocol_info=None):
        """Set a resource uri for this instance. If no resource exists, create
        a new one with the given protocol info.

        Args:
            uri (str): The resource uri.
            resource_nr (int): The index of the resource on which to set the
                uri. If it does not exist, a new resource is added to the list.
                Note that by default, only the uri of the first resource is
                used for playing the item.
            protocol_info (str): Protocol info for the resource. If none is
                given and the resource does not exist yet, a default protocol
                info is constructed as '[uri prefix]:*:*:*'.
        """
        try:
            self.resources[resource_nr].uri = uri
            if protocol_info is not None:
                self.resources[resource_nr].protocol_info = protocol_info
        except IndexError:
            if protocol_info is None:
                # create default protcol info
                protocol_info = uri[:uri.index(':')] + ':*:*:*'
            self.resources.append(DidlResource(uri, protocol_info))