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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 rar3_type(btype):
 """RAR3 type code as string."""

    if btype < rf.RAR_BLOCK_MARK or btype > rf.RAR_BLOCK_ENDARC:
        return "*UNKNOWN*"
    return block_strs[btype - rf.RAR_BLOCK_MARK]