Add GetObserverPriority as a workaround for VTK

[paskino]

We should add this code in the utils for vtk. See https://discourse.vtk.org/t/consume-a-vtk-event-in-python/13052/3

def GetObserverPriority(vtk_object, event_name: str) -> int:
    '''Given a vtk object and an event name, return the priority of the observer
    
    In Python it is impossible to get an observer from the object programmatically, 
    but the string representation of the object contains the observers with priority.

    This code reads the string representation and returns the priority as integer.
    '''
    string = str(vtk_object)

    ss = string.split("vtkObserver")

    eventObservers = []
    for s in ss:
        lines = s.split("\n")
        eo = {}
        for line in lines:
            try:
                k,v = line.split(":")
                k = k.strip()
                v = v.strip()
                if k in ['Event', 'EventName', 'Command', 'Priority', 'Tag']:
                    eo[k] = v
                    eventObservers.append(eo)
            except:
                pass

    for el in eventObservers:
        if el['EventName'] == event_name:
            return int(el['Priority'])