teams.rb

class Team 
include Neo4j::ActiveNode
  property :name, type: String
  has_one :out, :league, type: :PLAY_IN
end

class League 
  include Neo4j::ActiveNode
  property :name, type: String
  property :rank, type: Integer

  has_many :in, :teams, origin: :league
end

team = Team.create(name: 'Springfield Isotopes')
league = League.create(name: 'The Minor League')
team.league = league
# Same as:
# league.teams << team

# returns our league
team.league
# returns our team using the same relationship but from the other side
league.teams.first

# returns an AssociationProxy object, not executed until you call `to_a`, `first`, etc,...
match = league.teams.where(name: 'Springfield Isotopes')