# Functions
AddTags appends a tag to the tags field of ms.
AddTagsWithKey appends a tag to the key field of ms.
MapStrUnion creates a new MapStr containing the union of the key-value pairs of the two maps.
MergeFields merges the top-level keys and values in each source map (it does not perform a deep merge).
MergeFieldsDeep recursively merges the keys and values from `from` into `target`, either into ms itself (if underRoot == true) or into ms["fields"] (if underRoot == false).
# Variables
ErrKeyNotFound indicates that the specified key was not found.
# Type aliases
StringMap map参数.