Utility function to determine transformer functions for variants
    fields.

def _info_transformers(fields, transformers):
    """Utility function to determine transformer functions for variants
    fields."""
    if transformers is None:
        # no transformers specified by user
        transformers = dict()
    for f in fields:
        if f not in transformers:
            transformers[f] = config.DEFAULT_TRANSFORMER.get(f, None)
    return tuple(transformers[f] for f in fields)