code: function findAssertionSourceInTrace(trace) {
  
      var found = null;
  
      for (var i = 0, l = trace.length; i < l; ++i) {
        if (
          trace[i].file === stSkipStart.file &&
          trace[i].line >= stSkipStart.line &&
          trace[i].line <= stSkipEnd.line
        ) {
          break;
        }
        found = trace[i];
      }
  
      return found;
  
    }
docs: Find an assertion's likely 'source' by removing any references to twtl
  in the stack trace