25:T53d,import java.util.Collection; import java.util.Map; public class Graph { public Graph() { } public Graph(Map attributes) { } public Collection getNodes() { throw new UnsupportedOperationException("Delete this statement and write your own implementation."); } public Collection getEdges() { throw new UnsupportedOperationException("Delete this statement and write your own implementation."); } public Graph node(String name) { throw new UnsupportedOperationException("Delete this statement and write your own implementation."); } public Graph node(String name, Map attributes) { throw new UnsupportedOperationException("Delete this statement and write your own implementation."); } public Graph edge(String start, String end) { throw new UnsupportedOperationException("Delete this statement and write your own implementation."); } public Graph edge(String start, String end, Map attributes) { throw new UnsupportedOperationException("Delete this statement and write your own implementation."); } public Map getAttributes() { throw new UnsupportedOperationException("Delete this statement and write your own implementation."); } } 26:T524,import java.util.ArrayList; import java.util.Collection; import java.util.Collections; import java.util.List; import java.util.Map; public class Graph { private final List nodes = new ArrayList<>(); private final List edges = new ArrayList<>(); private final Map attributes; public Graph() { this.attributes = Collections.emptyMap(); } public Graph(Map attributes) { this.attributes = Map.copyOf(attributes); } public Collection getNodes() { return Collections.unmodifiableList(nodes); } public Collection getEdges() { return Collections.unmodifiableList(edges); } public Graph node(String name) { nodes.add(new Node(name)); return this; } public Graph node(String name, Map attributes) { nodes.add(new Node(name, attributes)); return this; } public Graph edge(String start, String end) { edges.add(new Edge(start, end)); return this; } public Graph edge(String start, String end, Map attributes) { edges.add(new Edge(start, end, attributes)); return this; } public Map getAttributes() { return attributes; } } 27:Tda6,