What is the basis for this scene in Peter Brook's Mahabharat

In Peter Brooks play/movie adaptation of Mahabharat the following conversation ensues between Krishna and Bhishma before the game of dice was to commence;[Given here below. Shortened/edited by me, but the theme remains the same.]

Krishna: Bhishma do me a favor. Whatever you see or hear in the course of the game, do not interrupt, in no circumstances.

Bhishma: But won't it be better to avoid the worst.

Krishna: What is the worst?

Bhishma: Destruction of dharma.

Krishna: And if your race has to be destroyed, so as to save dharma, would you be prepared to sacrifice your race?

[We need to remember here that Bhishma had vowed to protect his race at all costs and towards that goal remained celibate.]

Bhishma: [Bhishma entering into contemplation mood says;] This thought which is always with me has been disturbing my sleep and makes my heart pound all night along.

Krishna: That is why I ask you; do not intervene. Let each one go to his limit. [Saying so Krishna disappears.]

My query: Is this scene and its dialogues, just a dramatized adaptation of the original, because I don't find this in the original Vyasa Mahabharata. Or does it have its base in any of the other versions of the story mentioned in other ancient scriptures? What is the basis for this scene. Or is it just an imagination, written for the screenplay of Mahabharata by Peter Brook, Jean-Claude Carrière and Marie-Hélène Estienne. Can anyone throw some light on this? Which are the scriptures and books on which Peter Brook's Mahabharata is adapted from?

The link to Peter Brook's Mahabharata is here below;

The said scene begins exactly at 1:09:04.