Signals Notebook: How to limit the experiment access policy for specific groups that already have experiments without affecting other groups?

Description: There is a need to limit access of two groups so members can only read each other's experiments but not the experiments of the other three groups. The experiments do not have any fields that indicate the group they were made by.

Solution: 
1. For new experiments: Set a security policy rule using an attribute for the groups in the experiment templates and group associations. Please refer to this article: Signals Notebook: Is there a way to limit content access to experiments by group
2. For old experiments: 
  a. User can manually share the experiments only with the specific groups. Please refer to this article: Signals Notebook: Share an Experiment with other users in Signals 
  b. Administrator can share using the API endpoint POST/entities/{eid}/shares. Please refer to this article:  Signals Notebook: How to share an experiment using the API?