dedupe.py

def dedupe(original):
    """method to remove unnecessary ; and duplicate values"""
    value_set = set(filter(bool, map(lambda it: it.strip(), original.split(';'))))
    return '; '.join(list(value_set))

Actually it would have been 1 line in Java, very similar to what you have here, using the functional features of Java.

Let's see that line!