code: def pair_is_consistent(graph: BELGraph, u: BaseEntity, v: BaseEntity) -> Optional[str]:
      
      relations = {data[RELATION] for data in graph[u][v].values()}
  
      if 1 != len(relations):
          return
  
      return list(relations)[0]
docs: Return if the edges between the given nodes are consistent, meaning they all have the same relation.
  
      :return: If the edges aren't consistent, return false, otherwise return the relation type