MSFFormat.read_block

You're seeing just the function read_block, go back to MSFFormat module for more information.
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read_block(msf, index)

Attempt to read the block at the given index from the given MSF file. If a size parameter is given, the specified number of bytes will be read, otherwise the entire contents of the block will be read.

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read_block(msf_format, index, size)