YAML config file to New Python Model Format (NPMF)

[sbenthall]

With #1371, the New Python Model Format and the prototype YAML format developed in RLRO are nearly identical data structures.

This ticket is for implementing the compiler that consumes YAML and creates a valid Python object in NPMF.

As we have seen, mathematical expressions in YAML can be converted to useful Python using SymPy. Indeed, this was what Pablo originally did with Dolo. We can in HARK 1.0 provided similar functionality.

(There are some noted frustrating things about how SymPy changes the algebraic form of some expressions that it parses. These motivate the special parser in Dolo. However:

• We have not yet identified whether we need the special parser for our applications
• We have stronger ties to the SciPy ecosystem and might be able to advocate for changes to SymPy to accomodate us
• Since we have a programmable NPMF interface, in the worst case the user can just configure their model in Python and bypass SymPy/YAML issues. )