@Override
            protected void writeValueTo(Output output, int fieldNumber,
                    Object value, boolean repeated) throws IOException
            {
                if (!genericType.isAssignableFrom(value.getClass()))
                {
                    throw new RuntimeException(f.getDeclaringClass().getName() + 
                            "::" + f.getName() + " - " + value.getClass().getName() + 
                            " is not assignable to " + genericType.getName());
                }
                output.writeObject(fieldNumber, value, schemaV.getSchema(),
                        repeated);
            }
For lazy initialization called by {@link RuntimeFieldFactory}.
protostuff-runtime/src/main/java/io/protostuff/runtime/RuntimeCollectionFieldFactory.java