code: public Map<String, Object> asMap() {
          Map<String, Object> map = getBody().asMap();
          // add meta properties: ID, rev, deleted
          map.put("_id", id);
          if (revision != null) {
              map.put("_rev", revision);
          }
          if (this.isDeleted()) {
              map.put("_deleted", true);
          }
          return map;
      }
docs: <p>Returns the JSON body of the document revision as a {@code Map}
  object.</p>
  
  <p>This Map includes reserved fields such as {@code _id} and
  {@code _rev}. Changing the byte array may affect the {@code DocumentRevision},
  as only a shallow copy is returned.</p>
  
  @return the JSON body of the document revision as a {@code Map}
  object.