It's impossible to implement the chains.Chain interface because it depends on a private struct

[kraney]

Because ChainCallOption is defined as

type ChainCallOption func(*chainCallOption)

it's impossible to implement the Chains interface anywhere outside the chains package. You must support these options in the Call() method, but there is no way to read them. To do so, you would have to instantiate a struct that's private to the chains package.

[pnthang01]

Exactly, we need to make the struct public so we can make custom LLMChain from it. For now, I have to work around to make it work, that's painful.