<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def onlyOnce(fn):
    'Set up FN to only run once within an interpreter instance'
    def wrap(*args, **kwargs):
        if hasattr(fn, 'called'):
            return
        fn.called = 1
        return fn(*args, **kwargs)
    util.mergeFunctionMetadata(fn, wrap)
    return wrap