original_string: protected function isNullableKey($key)
      {
          if ( ! array_key_exists($key, $this->info->attributes)) {
              throw new RuntimeException(
                  "Foreign key '{$key}' defined for relation does not exist on model " . get_class($this->model())
              );
          }
  
          return (bool) $this->info->attributes[ $key ]->nullable;
      }
code: protected function isNullableKey($key)
      {
          if ( ! array_key_exists($key, $this->info->attributes)) {
              throw new RuntimeException(
                  "Foreign key '{$key}' defined for relation does not exist on model " . get_class($this->model())
              );
          }
  
          return (bool) $this->info->attributes[ $key ]->nullable;
      }
code_tokens: protected function isNullableKey ( $ key ) { if ( ! array_key_exists ( $ key , $ this -> info -> attributes ) ) { throw new RuntimeException ( "Foreign key '{$key}' defined for relation does not exist on model " . get_class ( $ this -> model ( ) ) ) ; } return ( bool ) $ this -> info -> attributes [ $ key ] -> nullable ; }
docstring: Returns whether attribute with key is known to be nullable.
  
  @param string $key
  @return bool
docstring_tokens: Returns whether attribute with key is known to be nullable .