Type Alias SequenceMessageKind

What a message of a sequence diagram is, as its arrow draws it.

• sync -- a call the sender waits on, a solid line with a filled head.
• async -- a message the sender does not wait on, an open head.
• reply -- a return, drawn dashed.
• create and destroy -- a message that brings a participant into being or ends it.
• note -- a note pinned over one participant or spanning several, which is read in its place in time like a message.