code: private void onSetGcGrace(CfDef cfDef, Properties cfProperties, StringBuilder builder)
      {
          String gcGraceSeconds = cfProperties.getProperty(CassandraConstants.GC_GRACE_SECONDS);
          if (gcGraceSeconds != null)
          {
              try
              {
                  if (builder != null)
                  {
                      appendPropertyToBuilder(builder, gcGraceSeconds, CassandraConstants.GC_GRACE_SECONDS);
                  }
                  else
                  {
                      cfDef.setGc_grace_seconds(Integer.parseInt(gcGraceSeconds));
                  }
              }
              catch (NumberFormatException nfe)
              {
                  log.error("GC_GRACE_SECONDS should be numeric type, Caused by: .", nfe);
                  throw new SchemaGenerationException(nfe);
              }
          }
      }
docs: On set gc grace.
  
  @param cfDef
  the cf def
  @param cfProperties
  the cf properties
  @param builder
  the builder