code: public AssemblyResponse cancelAssembly(String url)
              throws RequestException, LocalOperationException {
          Request request = new Request(this);
          return new AssemblyResponse(request.delete(url, new HashMap<String, Object>()));
      }
docs: cancels a running assembly.
  
  @param url full url of the Assembly.
  @return {@link AssemblyResponse}
  @throws RequestException if request to transloadit server fails.
  @throws LocalOperationException if something goes wrong while running non-http operations.