code: private boolean isCausal(KamEdge edge) {
          return edge.getRelationshipType() == RelationshipType.INCREASES
                  || edge.getRelationshipType() == RelationshipType.DIRECTLY_INCREASES
                  || edge.getRelationshipType() == RelationshipType.DECREASES
                  || edge.getRelationshipType() == RelationshipType.DIRECTLY_DECREASES;
      }
docs: returns true if the edge has one of the 4 causal relationship types.
  @param edge
  @return