8 files declare their use of DataProviderInterface in RESTful 7.2

AuthenticatedResource.php in src/Plugin/resource/AuthenticatedResource.php

Contains \Drupal\restful\Plugin\resource\AuthenticatedResource

CacheDecoratedResource.php in src/Plugin/resource/Decorators/CacheDecoratedResource.php

Contains \Drupal\restful\Plugin\resource\Decorators\CacheDecoratedResource

DataProviderComment.php in modules/restful_example/src/Plugin/resource/comment/DataProviderComment.php

Contains \Drupal\restful_example\Plugin\resource\comment\DataProviderComment.

DataProviderVariable.php in modules/restful_example/src/Plugin/resource/variables/DataProviderVariable.php

Contains \Drupal\restful_example\Plugin\resource\variables\DataProviderVariable.

DataProviderVariableInterface.php in modules/restful_example/src/Plugin/resource/variables/DataProviderVariableInterface.php

Contains \Drupal\restful_example\Plugin\resource\variables\DataProviderVariableInterface.

Resource.php in src/Plugin/resource/Resource.php

Contains \Drupal\restful\Plugin\resource\Resource.

ResourceDecoratorBase.php in src/Plugin/resource/Decorators/ResourceDecoratorBase.php

Contains \Drupal\restful\Plugin\resource\Decorators\ResourceDecoratorBase.

ResourceInterface.php in src/Plugin/resource/ResourceInterface.php

Contains \Drupal\restful\Plugin\resource\ResourceInterface.