Remove output specific variables to allow variables to be inputs to next steps.

def _clean_output(v):
    """Remove output specific variables to allow variables to be inputs to next steps.
    """
    out = copy.deepcopy(v)
    outb = out.pop("outputBinding", {})
    if "secondaryFiles" in outb:
        out["secondaryFiles"] = outb["secondaryFiles"]
    return out