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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 all_tokens(self, delimiter=' '):
 """ Return a list of all tokens occurring in the label-list. Args: delimiter (str):
 The delimiter used to split labels into tokens (see :meth:`audiomate.annotations.Label.tokenized`). Returns: :class:`set`: A set of distinct tokens. """

        tokens = set()

        for label in self:
            tokens = tokens.union(set(label.tokenized(delimiter=delimiter)))

        return tokens