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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 lemmas(lemma,pos=None):
 """Returns all the Lemma objects of which name is `lemma` and which have `pos` as part of speech. Parameters lemma : str Literal of the sought Lemma objects. pos : str, optional Part of speech of the sought Lemma objects. If None, matches any part of speech. Defaults to None Returns ------- list of Lemmas Lists all the matched Lemmas. """

    lemma = lemma.lower()
    return [lemma_obj
        for synset in synsets(lemma,pos)
        for lemma_obj in synset.lemmas()
        if lemma_obj.name.lower() == lemma]