HMSET key field value [field value ...]
Time complexity: O(N) where N is the number of fields being set.
Sets the specified fields to their respective values in the hash stored at
This command overwrites any specified fields already existing in the hash.
key does not exist, a new key holding a hash is created.
dragonfly> HMSET myhash field1 "Hello" field2 "World"
dragonfly> HGET myhash field1
dragonfly> HGET myhash field2