code: private void writeCustomField(CustomField field) throws IOException
     {
        if (field.getAlias() != null)
        {
           m_writer.writeStartObject(null);
           m_writer.writeNameValuePair("field_type_class", field.getFieldType().getFieldTypeClass().name().toLowerCase());
           m_writer.writeNameValuePair("field_type", field.getFieldType().name().toLowerCase());
           m_writer.writeNameValuePair("field_alias", field.getAlias());
           m_writer.writeEndObject();
        }
     }
docs: Write attributes for an individual custom field.
  Note that at present we are only writing a subset of the
  available data... in this instance the field alias.
  If the field does not have an alias we won't write an
  entry.
  
  @param field custom field to write
  @throws IOException