code: function ForkContext(idGenerator, upper, count) {
  		this.idGenerator = idGenerator;
  		this.upper = upper;
  		this.count = count;
  		this.segmentsList = [];
  	}
docs: ------------------------------------------------------------------------------ Public Interface ------------------------------------------------------------------------------ 
  A class to manage forking.
  
  @constructor
  @param {IdGenerator} idGenerator - An identifier generator for segments.
  @param {ForkContext|null} upper - An upper fork context.
  @param {number} count - A number of parallel segments.