get list of document in function*

### How to reproduce these conditions

**Sample name or URL where you found the bug**

**Failing Function code used (including require/import commands at the top)**

**Steps to set up and reproduce**

**Sample data pasted or attached as JSON (not an image)**

**Security rules used**

### Debug output

**Errors in the [console logs](https://console.firebase.google.com/project/_/functions/logs?search=&severity=DEBUG)**

**Screenshots**

### Expected behavior

### Actual behavior