code: public static function findRemovedTypes(
          Schema $oldSchema,
          Schema $newSchema
      ) {
          $oldTypeMap = $oldSchema->getTypeMap();
          $newTypeMap = $newSchema->getTypeMap();
  
          $breakingChanges = [];
          foreach (array_keys($oldTypeMap) as $typeName) {
              if (isset($newTypeMap[$typeName])) {
                  continue;
              }
  
              $breakingChanges[] = [
                  'type'        => self::BREAKING_CHANGE_TYPE_REMOVED,
                  'description' => "${typeName} was removed.",
              ];
          }
  
          return $breakingChanges;
      }
docs: Given two schemas, returns an Array containing descriptions of any breaking
  changes in the newSchema related to removing an entire type.
  
  @return string[][]