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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 restore(s, t):
 """ s is the source string, it can contain '.' t is the target, it's smaller than s by the number of '.'s in s Each char in s is replaced by the corresponding char in t, jumping over '.'s in s. 'XYZ.ABC' """

    t = (c for c in t)
    return ''.join(next(t) if not is_blacksquare(c) else c for c in s)