register() {
    for (var i = 0; i < arguments.length; ++i) {
      if (typeof arguments[i] === "function") {
        this.hooks.push(arguments[i]);
      } else {
        // unpack array
        for (var j = 0; j < arguments[i].length; ++j) {
          this.hooks.push(arguments[i][j]);
        }
      }
    }
  }
Adds a function to be run before a hook completes
@example this.content.register(function(){...});