(graph, visited)
return None
Return first unvisited node.
    
    @type  graph: graph
    @param graph: Graph.

    @type  visited: list
    @param visited: List of nodes.
    
    @rtype:  node
    @return: First unvisited node.
Return first unvisited node.
    
    @type  graph: graph
    @param graph: Graph.
Return first unvisited node . @type graph : graph @param graph : Graph .
def _first_unvisited(graph, visited):
    """
    Return first unvisited node.
    
    @type  graph: graph
    @param graph: Graph.

    @type  visited: list
    @param visited: List of nodes.
    
    @rtype:  node
    @return: First unvisited node.
    """
    for each in graph:
        if (each not in visited):
            return each
    return None
def _first_unvisited ( graph , visited ) : for each in graph : if ( each not in visited ) : return each return None