input
 terse
 strict
 indent
 recalculate-coordinates
 angle
 relative-angles
 flip
 flop
 show-carbons
 show-methyls
 hydrogens
 aromatic-circles
 fancy-bonds
 markers
 atom-numbers
 bond-scale
 bond-stretch
 wrap-chemfig
 submol-name
 entry-atom
 exit-atom
 cross-bond