Converts a tree to cherry tree -- needs review.

cherry_tree.py

def tree_to_cherry_tree(A):
    """
    Given the adj matrix of a tree, 
    produces a cherry t-tree that includes it. 
    
    Arguments:
    - adj: numpy array or sparse array, the adjacency matrix of the tree.
    
    Returns:
    - new_adj: numpy array or sparse array, the adjacency matrix of the cherry tree.
    """
    
    new_A = A.copy()
    n,m = new_A.shape
    for i in range(n):
        new_A[i,i] = -5
        
    V = set([i for i in range(len(A))])
    node1 = V.pop()    
    node2 = next((i for i, x in enumerate(list(A[node1, :])) if x), None) # x!= 0 for strict match
    V.remove(node2)

    for i in V:
        other_node = next((j for j, x in enumerate(list(A[i, :])) if x), None)
        not_connected = next((j for j, x in enumerate(list(new_A[i, :])) if x == 0), None)
        new_A[i,not_connected] = 1
        new_A[not_connected,i] = 1
        
    for i in range(n):
        new_A[i,i] = 0
        
    return new_A