code: public function findKey($key, $postVars)
      {
          $multiselectKey = str_replace('[]', '', $key);
          if (array_key_exists($key, $postVars)) {
              return $key;
          } else if (array_key_exists($multiselectKey, $postVars)) {
              return $multiselectKey;
          } else {
              return null;
          }
      }
docs: This fixes an issue where the Greenhouse API returns required multiselects as <field[]> but we require
  the user to submit it as <field>, thus making the system think the required field is not set.  This
  checks that either <field> or <field[]> is set, in order to work correctly but also be backward
  compatable in case external systems have already corrected for it.
  
  @params  Array   $key        The key to check for in $postVars
  @params  Array   $postVars   Greenhouse post parameters.
  @return  Mixed   string/null