anchor.diff:  * <<start,getting started>>
   * <<testing,testing>>
   * <<types,types>>
  -* <<ctors,construction>>
  +* <<ctors,constructors>>
   * <<axioms,axioms>>
   * <<keys,Keys, keychains, keylinks, dogtags>>
   * <<kinds,kinds>>
  
positive.code: (entity-map! [:A] {:a 1 :b 2})          ;; kinded ctor (see below)
  (entity-map! [:A/B :C] {:a 1 :b 2})          ;; kinded ctor (see below)
  (entity-map! :force [:A/B] {:a 9 :b 10}) ;; force replacement
  ----
  
  == [[[axioms]]structural axioms
  
negative.code: 
  These are represented in migae as `entity-map` and `keychain`, respectively.
  
  == [[ctors]]constructors
  
  We have three ways to construct PersistentEntityMap objects:
  
  