def add_model(self, ic, N=<NUM_LIT:1>, index=<NUM_LIT:0>):
if type(index) in [list,tuple]:<EOL><INDENT>if len(index) != N:<EOL><INDENT>raise ValueError('<STR_LIT>')<EOL><DEDENT><DEDENT>else:<EOL><INDENT>index = [index]*N<EOL><DEDENT>for idx in index:<EOL><INDENT>existing = self.get_system(idx)<EOL>tag = len(existing)<EOL>self.add_child(ModelNode(ic, index=idx, tag=tag))<EOL><DEDENT>
Should only be able to do this to a leaf node.

Either N and index both integers OR index is
list of length=N