Try to load a pymc trace from a path. If the path doesn't exist then generate the trace by calling fun.

make_trace.py

import arviz as az

def make_trace(path: str, fun: Callable, *args, **kwargs):
    """
    Try to load a pymc trace from a path. If the path doesn't exist then generate
    the trace by calling fun.

    Args:
        path: Path to Netcdf file.
        fun: Callable that returns a PyMC trace.
        *args, **kwargs: Passed to fun.
    """
    try:
        trace = az.from_netcdf(path)

    except FileNotFoundError:
        trace = fun(*args, **kwargs)
        trace.to_netcdf(path)

    return trace