code: public CMASnapshot fetchOneSnapshot(CMAEntry entry, String snapshotId) {
      assertNotNull(entry, "entry");
      assertNotNull(snapshotId, "snapshotId");
  
      final String entryId = getResourceIdOrThrow(entry, "entry");
      final String spaceId = getSpaceIdOrThrow(entry, "entry");
      final String environmentId = entry.getEnvironmentId();
  
      return service.fetchOneSnapshot(spaceId, environmentId, entryId, snapshotId).blockingFirst();
    }
docs: Fetch a specific snapshot of an entry.
  
  @param entry      the entry whose snapshot to be returned.
  @param snapshotId the snapshot to be returned.
  @return an array of snapshots.
  @throws IllegalArgumentException if entry is null.
  @throws IllegalArgumentException if entry's id is null.
  @throws IllegalArgumentException if entry's space id is null.
  @throws IllegalArgumentException if snapshotId is null.