Use this if you are using igraph from R
| isomorphisms {igraph} | R Documentation | 
Calculate all isomorphic mappings between the vertices of two graphs
isomorphisms(graph1, graph2, method = "vf2", ...)
graph1 | 
 The first graph.  | 
graph2 | 
 The second graph.  | 
method | 
 Currently only ‘vf2’ is supported, see
  | 
... | 
 Extra arguments, passed to the various methods.  | 
A list of vertex sequences, corresponding to all mappings from the first graph to the second.
Other graph isomorphism: 
count_isomorphisms(),
count_subgraph_isomorphisms(),
graph_from_isomorphism_class(),
isomorphic(),
isomorphism_class(),
subgraph_isomorphic(),
subgraph_isomorphisms()