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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 to_dc(data):
 """ Convert WA-KAT `data` to Dublin core XML. Args: data (dict):
 Nested WA-KAT data. See tests for example. Returns: unicode: XML with dublin core. """

    root = odict[
        "metadata": odict[
            "@xmlns:xsi": "http://www.w3.org/2001/XMLSchema-instance",
            "@xmlns:dc": "http://purl.org/dc/elements/1.1/",
            "@xmlns:dcterms": "http://purl.org/dc/terms/",
            "@xmlns:rdf": "http://www.w3.org/1999/02/22-rdf-syntax-ns#",
        ]
    ]

    # map metadata to the root element, skip None values
    for key, val in _convert_metadata(_remove_none(data)).iteritems():
        if val is None:
            continue

        if isinstance(val, basestring) and not val.strip():
            continue

        if isinstance(val, str):
            val = val.decode("utf-8")

        root["metadata"][key] = val

    return unparse(root, pretty=True, indent="    ")