GUI: Connection Probability

[gtdang]

Working on the Network configuration export I noticed that the GUI is not using the connection probability in any way.

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The connectivity only have a weight widget parameter.

The connectivity widget constructor is shown below. Notice the docstring mentions probability, but it is not in the box construct. It's a bit hard to read but the connectivity box is a vertical box (Vbox) composed of 3 elements:

1. HTML - Receptor label
2. w_text_input - Weight widget
3. HTML - Black horizontal bar https://github.com/jonescompneurolab/hnn-core/blob/a1c94ee2f83e3b7a432fb03daa659f25a05da98a/hnn_core/gui/gui.py#L935-L951

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The Problem A problem arises when initializing the new network from widget values. It tries to assign a probability from a widget that does not exist (see below). The vbox_key.children[2].value, is not a probability widget but the html widget that styles the black horizontal bar. So the network actually gets assigned a probability value of "<hr style='margin-bottom:5px'/>"! https://github.com/jonescompneurolab/hnn-core/blob/a1c94ee2f83e3b7a432fb03daa659f25a05da98a/hnn_core/gui/gui.py#L1650-L1653

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Solution I suppose the easiest solution is to just add the probability as a widget for all the connections. Does this make sense for all types of connections?