constructor(parseTree, isomeric = false) {
    this.vertices = Array();
    this.edges = Array();
    this.atomIdxToVertexId = Array();
    this.vertexIdsToEdgeId = {};
    this.isomeric = isomeric; // Used to assign indices to the heavy atoms.

    this._atomIdx = 0; // Used for the bridge detection algorithm

    this._time = 0;

    this._init(parseTree);
  }
The constructor of the class Graph.

@param {Object} parseTree A SMILES parse tree.
@param {Boolean} [isomeric=false] A boolean specifying whether or not the SMILES is isomeric.