A typical Probe Set ID has a suffix which provides further data about the Probe
Set. For example, the suffix in "os014912_f_at" is "_f_at", and the first
letter "f" conveys added information as described in the following key list:
_f (sequence family): Probe sets that correspond to sequences for which it was
not possible to pick a full set of 20 unique and/or shared
similarity-constrained probes.
_g (common groups): Probes chosen in region of overlap.
_s (similarity constraint): Probes set that corresponds to a small of unique
genes (<5%) that share identical sequence. Probes were chosen from a region
that is common to these genes.
_r (rules dropped): Designates sequences for which it was not possible to pick
a full set of unique probes.
_i (incomplete): Designates sequences for which there are fewer than 15 unique
probes.
