code: protected void setAdditionalInfoToEventCallBackStruct(EventCallBackStruct callback_struct,
                              String device_name, String attribute, String event_name,
                              String[]filters, EventChannelStruct channel_struct) throws DevFailed{
          
          String constraint_expr = buildConstraintExpr(device_name, attribute, event_name, filters);
          int filter_id = add_filter_for_channel(channel_struct, constraint_expr);
  
          callback_struct.filter_constraint = constraint_expr;
          callback_struct.filter_id = filter_id;
          callback_struct.consumer  = this;
      }
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