Ensures that all atoms in the molecule have a unique mapNo. Atoms that already have a mapNo keep it. Atoms without a mapNo are assigned the next available number starting from 1. Throws if the molecule contains duplicate mapNo values.
The molecule to process (modified in place)
Ensures that all atoms in the molecule have a unique mapNo. Atoms that already have a mapNo keep it. Atoms without a mapNo are assigned the next available number starting from 1. Throws if the molecule contains duplicate mapNo values.