undirected relationship

Each [:KNOWS] relationship is stored one way, from Ava to Ben and from Ben to Cleo. Projecting them undirected represents each as parallel relationships in opposite directions.

MATCH (source:Person)-[:KNOWS]->(target:Person)
RETURN gds.graph.project(
  'people',
  source,
  target,
  {},
  {undirectedRelationshipTypes: ['*']}
)

Degree centrality run against people scores Ben 2. Each relationship goes out of both of its nodes, so the one from Ava counts for Ben as much as the one to Cleo. Ava and Cleo each score 1.