<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 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)