code: private function getFilterForInList(IFilter $filter, $operation)
      {
          // Rewrite the IN operation to a rephrased term: "(x=a) OR (x=b) OR ...".
          $subRules = array();
          foreach ($operation['values'] as $varValue) {
              $subRules[] = array(
                  'property'  => $operation['property'],
                  'operation' => '=',
                  'value'     => $varValue
              );
          }
          $this->calculateSubfilter(array(
              'operation' => 'OR',
              'children'    => $subRules
          ), $filter);
      }
docs: Return the filter query for a "foo IN ('a', 'b')" filter.
  
  @param IFilter $filter    The filter to add the operations to.
  
  @param array   $operation The operation to convert.
  
  @return void
  
  @throws \RuntimeException When the operation can not be parsed.