docs: def _add_exac(self, variant_obj, gemini_variant):
          """Add the gmaf frequency
          
          Args:
              variant_obj (puzzle.models.Variant)
              gemini_variant (GeminiQueryRow)        
          """
          exac = gemini_variant['aaf_exac_all']
          if exac:
              exac = float(exac)
              variant_obj.add_frequency('ExAC', exac)
              logger.debug("Updating ExAC to: {0}".format(
                  exac))