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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 _group_get_hostnames(self, group_name):
 """ Recursively fetch a list of each unique hostname that belongs in or under the group. This includes hosts in children groups. """

        hostnames = []

        hosts_section = self._get_section(group_name, 'hosts')
        if hosts_section:
            for entry in hosts_section['entries']:
                hostnames.extend(self.expand_hostdef(entry['name']))

        children_section = self._get_section(group_name, 'children')
        if children_section:
            for entry in children_section['entries']:
                hostnames.extend(self._group_get_hostnames(entry['name']))

        return hostnames