:   '''[zlib] crc32''' ''data'' ?''initValue''?
Calculate the checksum of the bytearray ''data'' using the CRC-32 algorithm. 
The optional ''initValue'' is the seed value for the algorithm; 
if omitted, a standard default will be used.

** See also **

   * [CRC]
   * https://en.wikipedia.org/wiki/CRC-32%|%CRC-32 in Wikipedia%|%
   * https://guru.multimedia.cx/crc32-vs-adler32/%|%CRC32 vs. Adler32%|%
   * [zlib adler32]

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