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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 is_unit_or_unitstring(value):
 """must be an astropy.unit"""

    if is_unit(value)[0]:
        return True, value
    try:
        unit = units.Unit(value)
    except:
        return False, value
    else:
        return True, unit