get identifier() {
    if (typeof identifierCache[this.name] !== "string") {
      const identifier = `${camelize(this.name)}Id`;

      identifierCache[this.name] = identifier;
    }

    return identifierCache[this.name];
  }
The belongsTo association adds a fk to the owner of the association

@class BelongsTo
@extends Association
@constructor
@public
@hide