code: public function when(bool $test, $encodings): self
      {
          if (!$test || is_null($encodings)) {
              return $this;
          }
  
          if ($encodings instanceof \Closure) {
              return $encodings($this);
          }
  
          if (is_string($encodings)) {
              $encodings = Encoding::custom($encodings);
          }
  
          $encodings = $encodings instanceof Encoding ? [$encodings] : $encodings;
  
          return $this->push(...$encodings);
      }
docs: Push encodings if the truth test evaluates to true.
  
  @param bool $test
  @param Encoding|string|iterable|\Closure|null $encodings
  @return EncodingList