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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 get(self, id_or_url, default=None):
 """Fetch and return the spreadsheet with the given id or url. Args: id_or_url (str):
 unique alphanumeric id or URL of the spreadsheet Returns: New SpreadSheet instance or given default if none is found Raises: ValueError: if an URL is given from which no id could be extracted """

        if '/' in id_or_url:
            id = urls.SheetUrl.from_string(id_or_url).id
        else:
            id = id_or_url
        try:
            return self[id]
        except KeyError:
            return default