AxAIAnthropicContentBlockStartEvent
Defined in: https://github.com/ax-llm/ax/blob/04543e9e0873874640d5dbb158048393db35723c/src/ax/ai/anthropic/types.ts#L325
Defined in: https://github.com/ax-llm/ax/blob/04543e9e0873874640d5dbb158048393db35723c/src/ax/ai/anthropic/types.ts#L325