docs: function enterConcurrent(states, opts) {
      var sstate, dstates, i, j, ni, nj;
  
      if (!this.__isCurrent__ || opts.force) {
        trace.call(this, "State: [ENTER]  : " + this.path() + (this.__isCurrent__ ? ' (forced)' : ''));
        this.__isCurrent__ = true;
        callEnterHandlers.call(this, opts.context);
      }
  
      for (i = 0, ni = this.substates.length; i < ni; i++) {
        sstate  = this.substates[i];
        dstates = [];
  
        for (j = 0, nj = states.length; j < nj; j++) {
          if (findPivot.call(sstate, states[j]) === sstate) {
            dstates.push(states[j]);
          }
  
        }
        enter.call(sstate, dstates, opts);
      }
  
      return this;
    }