Error when using layer_simpleweighteddigraph and Layer function

[maishaoshao]

Describe the bug
Hello, I am trying to use the MultilayerGraphs package for network analysis. I just copIed the example code and tried to know more about the functions. Then there were errors.

To Reproduce
Steps to reproduce the behavior:

1. Go to 'https://github.com/JuliaGraphs/MultilayerGraphs.jl'
2. Scroll down to 'Layers and Interlayers' and copies the
3. Copy the code block: # Create a simple directed value layer and # Create a simple directed value layer
4. Run and See error

Expected behavior
A network graph.

Screenshots

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Additional context
Add any other context about the problem here.