AttributeError: module 'networkx' has no attribute 'to_numpy_matrix'

This error occurs when you try to use the `to_numpy_matrix` function from the `networkx` module, but the function is not found. This may be due to using an older version of the module where the function was not yet implemented, or it may have been removed in a newer version of the module.

To fix this error, you can try updating the `networkx` module to the latest version, or you can use an alternative method to convert the graph to a numpy matrix. One option is to use the `adjacency_matrix` function from the `scipy` module, which can be used to create a sparse matrix representation of the graph. Another option is to manually create a numpy matrix by iterating over the nodes and edges of the graph.