Ldap search: how to select users from a trusted tree?

Question

LDAP

there are 4 domains = 4 holding companies.
Trusts are made between domains. Third-party software (for example, synology in one of the domains) perfectly sees the tree of users from trusted domains and works with them.
Question: how to "pull" all users from all domains using ldap_search or other scripting tools (python-ldap) by accessing one of the domains? what filter?