adds a directed labeled edge to the graph . the end points of the edge are specified by vertex labels . new vertices are automatically identified and added to the graph . concode_field_sep List<VertexLabelType> vertexLabels concode_elem_sep Hashtable<VertexLabelType,Hashtable<VertexLabelType,EdgeLabelType>> globalEdgeLookup concode_field_sep List<VertexLabelType> getVertexLabels concode_elem_sep List<VertexLabelType> getSuccessors concode_elem_sep EdgeLabelType get concode_elem_sep boolean isVertexLabel concode_elem_sep void clear concode_elem_sep Hashtable<VertexLabelType,EdgeLabelType> checkForNewVertex concode_elem_sep void addVertex concode_elem_sep void remove