Update handler.py

Updated Handler to have better debugging output when encountering errors trying to generate mesh

Updated Handler with support for custom 'commands' and seperated code into methods for more efficient calling.

Update handler.py

Update handler.py

Update handler.py

Update handler.py

Update handler.py

Update handler.py

Update handler.py

Update handler.py

Update handler.py

Update handler.py

Update handler.py

Update handler.py

Update handler.py

Update handler.py

Update handler.py

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