How to confirm the content of ebt (elements by type)

[JXW-CN]

Mr/Ms/Mx,

I would like to report a minor issue to your attention. 
I have recently used the AutoMapper to construct the crosslinking polymer. 
But I have tried many times to confirm the content of ebt (elements by type), always prompting "AssertionError: EBT (elements by type) is missing values. Check that all types are present and separated with a space. " 
In addition, the ebt in the example of phenolic resin is H H C C O O, which I don't understand either. 

Hoping to get help.
Best wishes.