def get_wordnet_cascade(ling_relations):
  """
  Receives a list of linguistic relations (strings),
  and returns one of those linguistic relations with highest priority:
  copy > inflection > derivation > synonym > antonym >
  hypernym > hyponym > sister > cousin > None.
  """
  relation = None
  if 'copy' in ling_relations:
    relation = 'copy'
  elif 'inflection' in ling_relations:
    relation = 'inflection'
  elif 'derivation' in ling_relations:
    relation = 'derivation'
  elif 'synonym' in ling_relations:
    relation = 'synonym'
  elif 'antonym' in ling_relations:
    relation = 'antonym'
  elif 'hypernym' in ling_relations:
    relation = 'hypernym'
  elif 'similar' in ling_relations:
    relation = 'similar'
  elif 'hyponym' in ling_relations:
    relation = 'hyponym'
  elif any(lr.startswith('sister') for lr in ling_relations):
    sister_rels = [lr for lr in ling_relations if lr.startswith('sister')]
    assert sister_rels
    relation = sister_rels[0]
  elif any(lr.startswith('cousin') for lr in ling_relations):
    cousin_rels = [lr for lr in ling_relations if lr.startswith('cousin')]
    assert cousin_rels
    relation = cousin_rels[0]
  return relation