ManyToMany not in getEntityChangeSet

[langziyang]

i have to Entity,

//......
#[ORM\ManyToMany(targetEntity: Roles::class, inversedBy: 'employees')]
private Collection $roles;
//.....

when i change roles form 1 to 2, in then preUpdate listener, the PreUpdateEventArgs->getEntityChangeSet() is not get roles change.

why?

"doctrine/doctrine-bundle": "^2.12",
"doctrine/doctrine-migrations-bundle": "^3.3",
"doctrine/orm": "^3.2",