Function term_index 

pub(crate) fn term_index(argument: &Bound<'_, PyAny>) -> PyResult<IborIndex>

The projection key a Python argument names.

A str is a code the caller typed, and is checked against the registry. An Index is a value already in hand, and is taken at its word — there is no typo to catch in an object. Anything else is refused naming what the two accepted shapes are, rather than failing later as a missing curve. The term index a template is stated on: an Index value, constructed or resolved, or a registry code. Any other kind of index is refused by name.