"""
  Protocols for embedding backends (structural typing, no inheritance required).
  
  Used by the embedding service so that any backend (ClipAsServiceImageEncoder,
  ClipImageModel, etc.) can be used as long as it implements the same interface.
  """
  
  from typing import List, Optional, Protocol
  
  import numpy as np
  
  
  class ImageEncoderProtocol(Protocol):
      """Contract for image encoders used by the embedding service /embed/image endpoint."""
  
      def encode_image_urls(
          self,
          urls: List[str],
          batch_size: Optional[int] = None,

          normalize_embeddings: bool = True,

      ) -> List[Optional[np.ndarray]]:
          """
          Encode a list of image URLs to vectors.
  
          Returns:
              List of vectors (or None for failed items), same length as urls.
          """
          ...