Remove the specified members from the set stored at key.
Specified members that are not a member of this set are ignored.
If key does not exist, it is treated as an empty set and this command returns
0.
An error is returned when the value stored at key is not a set.
Examples
127.0.0.1:6379> SADD myset "one"
(integer) 1
127.0.0.1:6379> SADD myset "two"
(integer) 1
127.0.0.1:6379> SADD myset "three"
(integer) 1
127.0.0.1:6379> SREM myset "one"
(integer) 1
127.0.0.1:6379> SREM myset "four"
(integer) 0
127.0.0.1:6379> SMEMBERS myset
1) "two"
2) "three"