Determine whether two graphs are isomorphic

`tf = isisomorphic(`

returns logical
`G1,G2`

)`1`

(`true`

) if a graph isomorphism exists
between graphs `G1`

and `G2`

; otherwise, it
returns logical `0`

(`false`

).

`tf = isisomorphic(`

specifies additional options with one or more name-value pair arguments. For
example, you can specify `G1,G2`

,`Name,Value`

)`'NodeVariables'`

and a list of node
variables to indicate that the isomorphism must preserve these variables to be
valid.