Change equality difference metrics to optionally use squared error and to return a data frame.
Change equality difference metrics to optionally use squared error and to return a data frame.

This change can be synced to github via copybara once cl/179068458 and cl/178133832
 are submitted.

PiperOrigin-RevId: 178133913

conversationai/unintended-ml-bias-analysis,conversationai/unintended-ml-bias-analysis