code: public CMAEditorInterface fetchOne(String spaceId, String environmentId, String contentTypeId) {
      assertNotNull(spaceId, "spaceId");
      assertNotNull(environmentId, "environmentId");
      assertNotNull(contentTypeId, "contentTypeId");
  
      return service.fetchOne(spaceId, environmentId, contentTypeId).blockingFirst();
    }
docs: Get the editor interface by id, using the given space and environment.
  <p>
  This method will override the configuration specified through
  {@link CMAClient.Builder#setSpaceId(String)} and
  {@link CMAClient.Builder#setEnvironmentId(String)}.
  
  @param spaceId       the id of the space this environment is part of.
  @param environmentId the id of the environment this editor interface is valid on.
  @param contentTypeId the contentTypeId this editor interface is valid on.
  @return the editor interface for a specific content type on a specific space.
  @throws IllegalArgumentException if space id is null.
  @throws IllegalArgumentException if environment id is null.
  @throws IllegalArgumentException if content type id is null.