def []=(key, value)
      raise ArgumentError, "key must be string" unless key.instance_of?(String)
      raise ArgumentError, "value must be string" unless value.instance_of?(String)

      @root_node = update_and_delete_storage(
        @root_node,
        NibbleKey.from_string(key),
        value
      )

      update_root_hash
    end
def []=(key, value)
      raise ArgumentError, "key must be string" unless key.instance_of?(String)
      raise ArgumentError, "value must be string" unless value.instance_of?(String)

      @root_node = update_and_delete_storage(
        @root_node,
        NibbleKey.from_string(key),
        value
      )

      update_root_hash
    end
Set value of key.

 @param key [String]
 @param value [String]