Given an RNA string$s$, its bonding graph is a graph whose nodes
represent the symbols of $s$ arranged in order around a circle and whose edges are divided into two sets.
Solid adjacency edges connect adjacent symbols from $s$, whereas
dashed basepair edges connect all pairs {A, U} and {C, G}. See the figure below for
an example of a bonding graph on the RNA string $s$ = "UAGCGUGAUCAC".

A matching of basepair edges of this graph represents a way for the nucleotides
of a strand of RNA to base pair and form an RNA secondary structure.

We may also add edges {G, U} to the bonding graph in the case that we allow wobble base pairing.