Retrieves the stream records from a given shard.
Specify a shard iterator using the ShardIterator parameter. The shard iterator specifies the position in the shard from which you want to start reading stream records sequentially. If there are no stream records available in the portion of the shard that the iterator points to, GetRecords returns an empty list. Note that it might take multiple calls to get to a portion of the shard that contains stream records.
GetRecords can retrieve a maximum of 1 MB of data or 1000 stream records,
whichever comes first.