code: function Source(procedure, parameters) {
      abstractions.Composite.call(this, utilities.types.SOURCE, parameters);
      this.getProcedure = function() { return procedure; };
      return this;
  }
docs: PUBLIC FUNCTIONS 
  This constructor creates a new source code component with optional parameters that are
  used to parameterize its behavior.
  
  @param {Tree} procedure The procedure that is contained within the source code.
  @param {Parameters} parameters Optional parameters used to parameterize the source code.
  @returns {Source} A new source code component.