return an instance of `val` that is of type `datatype`.
    keep track of exceptions so we can produce meaningful error messages.

def val_factory(val, datatypes):
    """
    return an instance of `val` that is of type `datatype`.
    keep track of exceptions so we can produce meaningful error messages.
    """
    exceptions = []
    for dt in datatypes:
        try:
            if isinstance(val, dt):
                return val
            return type_handler_object(val, dt)
        except Exception as e:
            exceptions.append(str(e))
    # if we get here, we never found a valid value. raise an error
    raise ValueError('val_factory: Unable to instantiate {val} from types {types}. Exceptions: {excs}'.
                     format(val=val, types=datatypes, excs=exceptions))