code: public Collection<BoxFileVersion> getVersions() {
          URL url = VERSIONS_URL_TEMPLATE.build(this.getAPI().getBaseURL(), this.getID());
          BoxAPIRequest request = new BoxAPIRequest(this.getAPI(), url, "GET");
          BoxJSONResponse response = (BoxJSONResponse) request.send();
  
          JsonObject jsonObject = JsonObject.readFrom(response.getJSON());
          JsonArray entries = jsonObject.get("entries").asArray();
          Collection<BoxFileVersion> versions = new ArrayList<BoxFileVersion>();
          for (JsonValue entry : entries) {
              versions.add(new BoxFileVersion(this.getAPI(), entry.asObject(), this.getID()));
          }
  
          return versions;
      }
docs: Gets any previous versions of this file. Note that only users with premium accounts will be able to retrieve
  previous versions of their files.
  
  @return a list of previous file versions.