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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 variant_to_canonical_string(obj):
 """ Return a list containing the canonical string for the given object. The ``obj`` can be a list or a set of descriptor strings, or a Unicode string. If ``obj`` is a Unicode string, it will be split using spaces as delimiters. :param variant obj: the object to be parsed :rtype: str :raise TypeError: if the ``obj`` has a type not listed above """

    acc = [DG_ALL_DESCRIPTORS.canonical_value(p) for p in variant_to_list(obj)]
    acc = sorted([a for a in acc if a is not None])
    return u" ".join(acc)