Add the gmaf frequency
        
        Args:
            variant_obj (puzzle.models.Variant)
            gemini_variant (GeminiQueryRow)

def _add_gmaf(self, variant_obj, gemini_variant):
        """Add the gmaf frequency
        
        Args:
            variant_obj (puzzle.models.Variant)
            gemini_variant (GeminiQueryRow)
        
        """
        max_af = gemini_variant['max_aaf_all']
        if max_af:
            max_af = float(max_af)
            if max_af != -1.0:
                variant_obj.set_max_freq(max_af)