Allow for isomorphism check for reactions with 3 reactants.
Allow for isomorphism check for reactions with 3 reactants.

Some reactions in GRI-Mech and probably other reaction libraries have this.
faribas/RMG-Py,KEHANG/RMG-Py,pierrelb/RMG-Py,KEHANG/RMG-Py,enochd/RMG-Py,enochd/RMG-Py,comocheng/RMG-Py,faribas/RMG-Py,chatelak/RMG-Py,nickvandewiele/RMG-Py,nickvandewiele/RMG-Py,chatelak/RMG-Py,nyee/RMG-Py,comocheng/RMG-Py,pierrelb/RMG-Py,nyee/RMG-Py