Bio::FeatureIO is an iterator subsystem for genomic sequence features.

Bio::FeatureIO is a handler module for the formats in the FeatureIO set (eg,
Bio::FeatureIO::GFF). It is the officially sanctioned way of getting at the
format objects, which most people should use.

The Bio::FeatureIO system can be thought of like biological file handles. They
are attached to filehandles with smart formatting rules (eg, GFF format, or BED
format) and can either read or write feature objects (Bio::SeqFeature objects,
or more correctly, Bio::FeatureHolderI implementing objects, of which
Bio::SeqFeature is one such object). If you want to know what to do with a
Bio::SeqFeatureI object, read Bio::SeqFeatureI.

The idea is that you request a stream object for a particular format. All the
stream objects have a notion of an internal file that is read from or written
to. A particular FeatureIO object instance is configured for either input or
output. A specific example of a stream object is the Bio::FeatureIO::gff object.