Not sure how much this is still WIP, but I've wanted to ask this before, and you seem to working on the relevant code: Since the YAML parser uses introspection to get the call signature of methods, it means that you can't use any built-in functions or NumPy ufuncs in a YAML file, which means things such as
```
{
  dim1: &dim1 5,
  dim2: !obj:pow(*dim1, 2)
}
```
don't work. Could we add support for ufuncs? They expose the number of arguments with the `.nin` attribute I think. Built-in functions are more complicated. I think you need to parse the docstring to get the number of arguments, but we could at least raise a more informative warning (I'm guessing right now it will just given an `AttributeError` saying that `__code__` doesnt exist?)

Also, any reason you are parsing arguments this way instead of using `inspect.getargspec`?