# Functions
DecodeKeyValue returns the original key and value corresponding to the encoded data in k, v.
FromContext returns the MD in ctx if it exists.
Join joins any number of MDs into a single MD.
New creates a MD from given key-value map.
NewContext creates a new context with md attached.
Pairs returns an MD formed by the mapping of key, value ..
# Type aliases
MD is a mapping from metadata keys to values.