is_edge_loop(graph, edge)

# Create a graph that has multiple
# loop edges
graph <-
  create_graph() %>%
  add_path(n = 4) %>%
  add_edge(
    from = 1,
    to = 1) %>%
  add_edge(
    from = 3,
    to = 3)

# Get the graph's internal
# edge data frame
graph %>% get_edge_df()

# Determine if edge `4` is
# a loop edge
graph %>% is_edge_loop(edge = 4)

# Determine if edge `2` is
# a loop edge
graph %>% is_edge_loop(edge = 2)