various modifications

[Martinus-Maximus]

• created classes Label, EdgeLabel, NodeLabel
• created method add_label(..) for inserting multiple labels at various positions in a Node
• created method add_label(..) for inserting multiple labels at various positions in a Edge
• added detailed error messages

[bockor]

Howdy -- Why I you inserting the from future import print_function line into your demo script ? I don' understand, is this really required ?

[Martinus-Maximus]

Hi Bockor,

I just took the UML Example (https://github.com/jamesscottbrown/pyyed/blob/master/examples/demo-uml.py) and modified it a little bit :)

In my view it is not necessary.

[jamesscottbrown]

Thank you for this contribution - this looks like a useful feature addition.