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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 fetch(cls, client, symbol):
 """ fetch data for stock """

        assert(type(symbol) is str)

        url = ("https://api.robinhood.com/instruments/?symbol={0}".
               format(symbol))
        data = client.get(url)
        return data["results"][0]