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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 within_history(rev, windowdict):
 """Return whether the windowdict has history at the revision."""

    if not windowdict:
        return False
    begin = windowdict._past[0][0] if windowdict._past else \
            windowdict._future[-1][0]
    end = windowdict._future[0][0] if windowdict._future else \
          windowdict._past[-1][0]
    return begin <= rev <= end