Check if Object is a Distance Object
Examples
left <- data.frame(id = 1:3, x = c(1, 2, 3))
right <- data.frame(id = 4:6, x = c(1.1, 2.1, 3.1))
dist_obj <- compute_distances(left, right, vars = "x")
is_distance_object(dist_obj) # TRUE
is_distance_object(list()) # FALSE