'Describes the specified stream.
The information about the stream includes its current status,
its Amazon Resource Name (ARN), and an array of shard objects.
For each shard object, there is information about the hash key
and sequence number ranges that the shard spans, and the IDs
of any earlier shards that played in a role in creating the
shard. A sequence number is the identifier associated with
every record ingested in the Amazon Kinesis stream. The
sequence number is assigned when a record is put into the
stream.
You can limit the number of returned shards using the `Limit`
parameter. The number of shards in a stream may be too large
to return from a single call to `DescribeStream`. You can
detect this by using the `HasMoreShards` flag in the returned
output. `HasMoreShards` is set to `True` when there is more
data available.
`DescribeStream` is a paginated operation. If there are more
shards available, you can request them using the shard ID of
the last shard returned. Specify this ID in the
`ExclusiveStartShardId` parameter in a subsequent request to
`DescribeStream`.
`DescribeStream` has a limit of 10 transactions per second per
account.
:type stream_name: string
:param stream_name: The name of the stream to describe.
:type limit: integer
:param limit: The maximum number of shards to return.
:type exclusive_start_shard_id: string
:param exclusive_start_shard_id: The shard ID of the shard to start
with.'

def describe_stream(self, stream_name, limit=None, exclusive_start_shard_id=None):

    params = {'StreamName': stream_name}
    if (limit is not None):
        params['Limit'] = limit
    if (exclusive_start_shard_id is not None):
        params['ExclusiveStartShardId'] = exclusive_start_shard_id
    return self.make_request(action='DescribeStream', body=json.dumps(params))
