Provides detailed information on isostericity of RNA basepairs. All data is extracted from csv files which were created from supplemental files in:
Frequency and isostericity of RNA base pairs Jesse Stombaugh, Craig L. Zirbel, Eric Westhof, and Neocles B. Leontis Nucl. Acids Res. (2009) doi:10.1093nargkp011
Methods to determine the isostericity classes for a given basepair type, or alternatively which basepair types are in a certain isostericity class.
TODO This requires a major cleanup: right now we are handling
class descriptors, but we should really be newtype-wrapping or create enum
To which classes does a basepair+type belong
What basepairs+type are in a particular class