code: def build_decryption_materials_cache_key(partition, request):
      
      hasher = _new_cache_key_hasher()
      _partition_hash = _partition_name_hash(hasher=hasher.copy(), partition_name=partition)
      _algorithm_info = request.algorithm.id_as_bytes()
      _edks_hash = _encrypted_data_keys_hash(hasher=hasher.copy(), encrypted_data_keys=request.encrypted_data_keys)
      _ec_hash = _encryption_context_hash(hasher=hasher.copy(), encryption_context=request.encryption_context)
  
      hasher.update(_partition_hash)
      hasher.update(_algorithm_info)
      hasher.update(_edks_hash)
      hasher.update(_512_BIT_PAD)
      hasher.update(_ec_hash)
      return hasher.finalize()
docs: Generates a cache key for a decrypt request.
  
      :param bytes partition: Partition name for which to generate key
      :param request: Request for which to generate key
      :type request: aws_encryption_sdk.materials_managers.DecryptionMaterialsRequest
      :returns: cache key
      :rtype: bytes