code: private void writeEntityContainer(EntityContainer entityContainer) throws XMLStreamException {
  
          xmlWriter.writeStartElement(ENTITY_CONTAINER);
          xmlWriter.writeAttribute(NAME, entityContainer.getName());
          for (EntitySet entitySet : entityContainer.getEntitySets()) {
              entitySetWriter.write(entitySet);
          }
          for (Singleton singleton : entityContainer.getSingletons()) {
              singletonWriter.write(singleton);
          }
          xmlWriter.writeEndElement();
      }
docs: Write the 'Entity Container'.
  <p>
  Note: The entity container is written only for the 'Schema' which namespace matches the name of the entity
  container itself. This entity container contains the types for all the schemas contained by the Entity Data
  Model though.
  </p>
  
  @param entityContainer The 'Entity Container' to write.
  @throws XMLStreamException