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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def write_file(writeFunc, index, existing, x):
 """Write a file into the Toil jobstore. 'existing' is a set of files retrieved as inputs from toil_get_file. This ensures they are mapped back as the same name if passed through. """

    # Toil fileStore reference
    if x.startswith("toilfs:"):
        return x
    # File literal outputs with no path, we don't write these and will fail
    # with unsupportedRequirement when retrieving later with getFile
    elif x.startswith("_:"):
        return x
    else:
        x = existing.get(x, x)
        if x not in index:
            if not urlparse.urlparse(x).scheme:
                rp = os.path.realpath(x)
            else:
                rp = x
            try:
                index[x] = "toilfs:" + writeFunc(rp)
                existing[index[x]] = x
            except Exception as e:
                cwllogger.error("Got exception '%s' while copying '%s'", e, x)
                raise
        return index[x]