def getSizeOfVST(vst):
    """
    Description: Return the size of the vector space of an vst variable.
    Look for the first existing vector of the vst and get its size.
    NB: Used only to not have to pass the size of the vst as a parameter.
    """
    size = 0
    for key in vst:
        if vst[key] is not None:
            #size = vst[key].size
            size = len(vst[key])
            break
    return size