anchor.diff:  
   This might produce something like `[:Foo/Bar :Baz/7]`.  The numeric id
   will be generated by the Datastore - see
  -[Assigning identifiers](https://cloud.google.com/appengine/docs/java/datastore/entities#Java_Assigning_identifiers).
  +link:https://cloud.google.com/appengine/docs/java/datastore/entities#Java_Assigning_identifiers[Assigning identifiers].
   
   
   # keys and the datastore
  
positive.code: ancestor path), use ds/key-name.  ("name" is reserved for getting the
  name component of a Key node).
  
  [Note that the keys in a keychain need not be associated with actual Entities in the datastore.]
  
  Migae uses keywords to encode Kinds and Identifiers.  The native
  datastore uses String for Kinds, and either String or Long for
  
negative.code: 
  Used as a query specification, this would match all Entities having
  kind `:Genus` and having parent Key `Subfamily("Felinae")` - the
  family link:https://en.wikipedia.org/wiki/Felinae[Felinae] includes, in
  addition to genus _Felis_, _Leopardus_, _Lynx_, _Puma_, and several
  others, so this might match `[:Subfamily/Felinae :Genus/Felis]`,
  `[:Subfamily/Felinae :Genus/Leopardus]`, etc.
  