code: protected function getPickerInputField($value, $attributes='')
  	{
  		$id = is_numeric($value) ? $value : md5($value);
  
  		switch ($this->strPickerFieldType)
  		{
  			case 'checkbox':
  				return ' <input type="checkbox" name="picker[]" id="picker_'.$id.'" class="tl_tree_checkbox" value="'.StringUtil::specialchars(\call_user_func($this->objPickerCallback, $value)).'" onfocus="Backend.getScrollOffset()"'.Widget::optionChecked($value, $this->arrPickerValue).$attributes.'>';
  
  			case 'radio':
  				return ' <input type="radio" name="picker" id="picker_'.$id.'" class="tl_tree_radio" value="'.StringUtil::specialchars(\call_user_func($this->objPickerCallback, $value)).'" onfocus="Backend.getScrollOffset()"'.Widget::optionChecked($value, $this->arrPickerValue).$attributes.'>';
  		}
  
  		return '';
  	}
docs: Return the picker input field markup
  
  @param string $value
  @param string $attributes
  
  @return string