is_namespace()
Return True if name binding introduces new namespace.
If the name is used as the target of a function or class statement, this will be true.
For example:
>>> table = symtable.symtable("def some_func(): pass", "string", "exec")
>>> table.lookup("some_func").is_namespace()
True
Note that a single name can be bound to multiple objects. If the result is True, the name may also be bound to other objects, like an int or list, that does not introduce a new namespac