code: public void setAvailableInputColumns(final Collection<InputColumn<?>> inputColumns) {
          final InputColumn<?>[] items = new InputColumn<?>[inputColumns.size() + 1];
          int index = 1;
          for (final InputColumn<?> inputColumn : inputColumns) {
              items[index] = inputColumn;
              index++;
          }
          final DefaultComboBoxModel<InputColumn<?>> model = new DefaultComboBoxModel<>(items);
          _comboBox.setModel(model);
      }
docs: Called by the parent widget to update the list of available columns
  
  @param inputColumns