A dictionary of filters to apply to retrieve memories. Available fields are: user_id, agent_id, app_id, run_id, created_at, updated_at, categories, keywords. Supports logical operators (AND, OR) and comparison operators (in, gte, lte, gt, lt, ne, contains, icontains, *). For categories field, use 'contains' for partial matching (e.g., {"categories": {"contains": "finance"}}) or 'in' for exact matching (e.g., {"categories": {"in": ["personal_information"]}}).