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  package org.apache.cayenne.graph;
  
  import java.util.Collection;
  
  /**
   * Represents a generic "managed" graph with nodes mapped by their ids. Inherited
   * GraphChangeHandler methods are intended as callbacks for graph node objects to notify
   * graph of their changes.
   * 
   * @since 1.2
   */
  public interface GraphManager extends GraphChangeHandler {
  
      /**
       * Returns a graph node given an id.
       */
      Object getNode(Object nodeId);
  
      /**
       * "Registers" a graph node, usually storing the node in some internal map using its
       * id as a key.
       */
      void registerNode(Object nodeId, Object nodeObject);
  
      /**
       * "Unregisters" a graph node, forgetting any information associated with nodeId.
       */
      Object unregisterNode(Object nodeId);
  
      /**
       * Returns all graph nodes registered with GraphManager.
       */
      Collection<Object> registeredNodes();
  }
  