Expand__to_dot variable cannot be used to control the behavior

[samv-yazzoom]

Hello,

This pull request: #809 moved the default for _expand__to_dot to a variable.
At load time, the default for _expand__to_dot will already be set to True. Overwriting EXPAND__TO_DOT after the import has not impact.

The variable would be usable if the default is resolved in the function definition.

[miguelgrinberg]

Duplicate of #1586