Returns a shard iterator. A shard iterator provides information about how to retrieve the stream records from within a shard. Use the shard iterator in a subsequent GetRecords request to read the stream records from the shard.
A shard iterator expires 15 minutes after it is returned to the requester.
/// An error occurred on the server side.
///
/// The operation tried to access a nonexistent stream.
///
/// The operation attempted to read past the oldest stream record in a shard.
///
///
///
/// In DynamoDB Streams, there is a 24 hour limit on data retention. Stream records whose
/// age exceeds this limit are subject to removal (trimming) from the stream. You might
/// receive a TrimmedDataAccessException if:
///
///
///
/// You request a shard iterator with a sequence number older than the trim point (24
/// hours).
///
///
///
/// You obtain a shard iterator, but before you use the iterator in a GetRecords
/// request, a stream record in the shard exceeds the 24 hour period and is trimmed. This
/// causes the iterator to access a record that no longer exists.
///
///