"""Core funtionality for chemical graphmachine engine.

chem_gm.core sub-package includes the following modules :
 - atoms
 - bonds
 - gmconstst
 - GMmodel
 - gmprograms
 - gmtoolbox
 - gmutils
 - graphmachineworkshop
 - metamolecule
 - smilexer
 - smiparserspec
 - smitokens
"""