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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def require_user(wa, email):
 """Require that the user has an account"""

    cache_key = 'user-list'
    try:
        # Get the cached value
        data = userCache[cache_key]
    except KeyError:
        # If we hit a key error above, indicating that
        # we couldn't find the key, we'll simply re-request
        # the data
        data = wa.users.loadUsers()
        userCache[cache_key] = data

    return AssertUser([x for x in data if x.username == email])