NameError: name 'Graph' is not defined

Question

`def grid_Graph(m, k=8, corners=False):

'''
To create adjacency matrix as per Defferrard et al. 2016
'''
z = Graph.grid(m)
dist, idx = Graph.distance_sklearn_metrics(z, k=k, metric='euclidean')

A = Graph.adjacency(dist, idx)

# Connections are only vertical or horizontal on the grid.
# Corner vertices are connected to 2 neightbors only.
if corners:
    import scipy.sparse
    A = A.toarray()
    A[A < A.max()/1.5] = 0
    A = scipy.sparse.csr_matrix(A)
    print('{} edges'.format(A.nnz))

print("{} > {} edges".format(A.nnz//2, k*m**2//2))
return A

def draw_Graph(A, m=32, ax=None, spring_layout=False, size_factor=10): '''给定邻接矩阵(A)画图， 可选择使用 spring_layout。 ''' 断言 m**2 == A.shape[0] == A.shape[1] # 创建 nx.Graph 对象 G = nx.from_scipy_sparse_matrix(A) print('节点数：%d；边数：%d' %
(G.number_of_nodes(), G.number_of_edges())) 网格坐标 = Graph.grid(m)

if spring_layout:
    # remove nodes without edges
    nodes_without_edges = [n for n, k in  G.degree() if k == 0]
    G.remove_nodes_from(nodes_without_edges)
    print('After removing nodes without edges:')
    print('Number of nodes: %d; Number of edges: %d' % \
          (G.number_of_nodes(), G.number_of_edges()))

z = Graph.grid(m)

# initial positions
pos = {n: z[n] for n in G.nodes()} 

if spring_layout:
    pos = nx.spring_layout(G, 
                           pos=pos,
                           iterations=200)

ax = nx.draw(G, pos,
             node_size=[G.degree(n) * size_factor for n in G.nodes()],
             ax=ax
            )
return ax

A = grid_Graph(28, k=8) plt.imshow(A.todense()) `