Base64 decode command line

Base64 decode command line I would like to write a bash script to decode a base64 string. For example I type decode QWxhZGRpbjpvcGVuIHNlc2FtZQ== and it prints Aladdin:open sesame and returns to the prompt. So far I have tried a simple bash file containing python -m base64 -d $1 but this command expects a filename not a string. ................
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