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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 contrib_xref(contrib_tag, ref_type):
 """ Given a contrib tag, look for an xref tag of type ref_type directly inside the contrib tag """

    aff_tags = []
    for child_tag in contrib_tag:
        if (child_tag and child_tag.name and child_tag.name == "xref"
            and child_tag.get('ref-type') and child_tag.get('ref-type') == ref_type):
            aff_tags.append(child_tag)
    return aff_tags