text: 0             0       15  on_llm_start  OpenAI     3       2     1       0         0             0       16  on_llm_start  OpenAI     3       2     1       0         0             0       17  on_llm_start  OpenAI     3       2     1       0         0             0       18    on_llm_end     NaN     4       2     2       0         0             0       19    on_llm_end     NaN     4       2     2       0         0             0       20    on_llm_end     NaN     4