Redis Cluster pipeline "exists" command error: unsupported operand type(s) for +=: 'int' and 'ClusterPipeline'

Version: redis-py version 4.1.4 and Redis version 6.2.6

Platform: Python 3.9.9 on Red Hat Enterprise Linux release 8.5

Description: We are testing the new "redis.cluster" module but when we execute the following test script:

from redis.cluster import RedisCluster

# Host "redis" is the boostrap node for the cluster
connection = RedisCluster.from_url("redis://redis:6379")

with connection.pipeline() as pipeline:
    pipeline.exists("test_key")
    # pipeline returns a list of responses
    # https://github.com/redis/redis-py#pipelines
    print(pipeline.execute()[-1])

It errors with the following stack trace:

$ python cluster-test.py
Traceback (most recent call last):
  File "/opt/apps/app_root/cluster-test.py", line 6, in <module>
    pipeline.exists("test_key")
  File "/opt/apps/app_venv/lib/python3.9/site-packages/redis/commands/cluster.py", line 108, in exists
    return self._split_command_across_slots("EXISTS", *keys)
  File "/opt/apps/app_venv/lib/python3.9/site-packages/redis/commands/cluster.py", line 98, in _split_command_across_slots
    total += self.execute_command(command, *slot_keys)
TypeError: unsupported operand type(s) for +=: 'int' and 'ClusterPipeline'

I tried to investigate the source code of cluster.py myself, but it's not really clear to me what the return type of self.execute_command is and why it would be ClusterPipeline in this case.

Is this a bug or are we doing something wrong?