code: def element_id_by_label(browser, label):
      
      label = ElementSelector(browser,
                              str('//label[contains(., %s)]' %
                                  string_literal(label)))
      if not label:
          return False
      return label.get_attribute('for')
docs: The ID of an element referenced by a `label`s ``for`` attribute. The label
      must be visible.
  
      :param browser: ``world.browser``
      :param label: label text to return the referenced element for
  
      Returns: ``for`` attribute value