code: public AbstractNode getChild(Interval<T> interval) throws MIDDException {
          for (AbstractEdge<T> e : this.edges) {
              if (e.containsInterval(interval)) {
                  return e.getSubDiagram();
              }
          }
          return null;
      }
docs: Return the child of the current node with equivalent interval on its incoming edge.
  
  @param interval The interval which is the subset of the interval in the incoming edge
  @return null if no matching edge found.