fix ArrowDecoder.decode to return instead of yield

src/gluonts/dataset/arrow/dec.py

@@ -32,7 +32,7 @@ def from_schema(cls, schema):
  )
 
  def decode(self, batch, row_number: int):
- yield from self.decode_batch(batch.slice(row_number, row_number + 1))
+ return next(self.decode_batch(batch.slice(row_number, row_number + 1)))
 
  def decode_batch(self, batch):
  for row in batch.to_pandas().to_dict("records"):