code: function (name, table, opts) {
              opts = opts || {};
              opts = isHash(table) ? merge({}, table, opts) : isString(table) ? merge({table:table}, opts) : opts;
              if (Array.isArray(name)) {
                  return this.__compositeForeignKey(name, opts);
              } else {
                  return this.column(name, "integer", opts);
              }
          }
docs: Add a foreign key in the table that references another table to the DDL. See {@link patio.SchemaGenerator#column{
  for options.
  
  @example
  DB.createTable("flight_leg", function () {
  this.primaryKey("id");
  this.scheduled_departure_time("time");
  this.scheduled_arrival_time("time");
  this.foreignKey("departure_code", "airport", {key:"airport_code", type : String, size : 4});
  this.foreignKey("arrival_code", "airport", {key:"airport_code", type : String, size : 4});
  this.foreignKey("flight_id", "flight", {key:"id"});
  });