<｜begin▁of▁sentence｜>### Instruction:
Given a custom shape name that is not recognized by the igraph library, how can you use the resolve_default method from the ShapeDrawerDirectory to either retrieve a corresponding shape drawer class or handle an unknown shape name?
### Response:
from igraph.drawing import shape_drawer_directory

# Assume 'my_custom_shape' is not a known shape name
custom_drawer_class = shape_drawer_directory.resolve_default('my_custom_shape', None)

if custom_drawer_class:
    print(f'Custom drawer class found: {custom_drawer_class}')
else:
    print('The shape name is unknown. No custom drawer class found.')
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