A class representing the 79 E-state atom types in terms of SMARTS.
These fragments were originally described in [Hall, L.H. and Kier, L.B.
, Electrotopological State Indices for Atom Types: A Novel Combination of Electronic, Topological, and Valence State Information, Journal of Chemical Information and Computer Science, 1995, 35:1039-1045, doi:10.1021/ci00028a014] and were
converted into SMARTS forms by the RDKit project