docs: def validate_request_partition_key(self, request):
          '''
          Validates that all requests have the same PartitiionKey. Set the
          PartitionKey if it is the first request for the batch operation.
  
          request:
              the request to insert, update or delete entity
          '''
          if self.batch_partition_key:
              if self.get_request_partition_key(request) != \
                  self.batch_partition_key:
                  raise AzureBatchValidationError(_ERROR_INCORRECT_PARTITION_KEY_IN_BATCH)
          else:
              self.batch_partition_key = self.get_request_partition_key(request)