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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_group_key_line(self, data, key):
 """Get the next group-style key's line number. :param data: string to parse :param key: the key category :returns: the found line number else -1 """

        idx = -1
        for i, line in enumerate(data.splitlines()):
            if isin_start(self.groups[key], line):
                idx = i
        return idx