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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 remove_stopwords(self, tokens):
 """Remove all stopwords from a list of word tokens or a string of text."""

        if isinstance(tokens, (list, tuple)):
            return [word for word in tokens if word.lower() not in self._stopwords]
        else:
            return ' '.join(
                [word for word in tokens.split(' ') if word.lower() not in self._stopwords]
            )