1 - The map output files are always of the type SequenceFileFormat?
2 - The means that it contains a header with the following files?
# version - A byte array: 3 bytes of magic header 'SEQ', followed by 1
byte of actual version no. (e.g. SEQ4 or SEQ6)
# keyClassName - String
# valueClassName - String
# compression - A boolean which specifies if compression is turned on
for keys/values in this file.
# blockCompression - A boolean which specifies if block compression is
turned on for keys/values in this file.
# compressor class - The classname of the CompressionCodec which is
used to compress/decompress keys and/or values in this SequenceFile
(if compression is enabled).
# metadata - SequenceFile.Metadata for this file (key/value pairs)
# sync - A sync marker to denote end of the header.