key is the first key to delete in the range.

If prev_kv is set, etcd gets the previous key-value pairs before deleting it. The previous key-value pairs will be returned in the delete response.

range_end is the key following the last key to delete for the range [key, range_end). If range_end is not given, the range is defined to contain only the key argument. If range_end is one bit larger than the given key, then the range is all the keys with the prefix (the given key). If range_end is '\0', the range is all keys greater than or equal to the key argument.