I'm trying to list budget policies using the parameter "filter_by" to filter policies that start with "aaaa" but I'm getting an error  "400 Bad Request"

{'error_code': 'MALFORMED_REQUEST', 'message': "Could not parse request object: Expected 'START_OBJECT' not 'VALUE_STRING'\n at [Source: REDACTED (`StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION` disabled); line: 1, column: 15]\n at [Source: UNKNOWN; line: 1, column: 15]", 'details': [{'@type': 'type.googleapis.com/google.rpc.RequestInfo', 'request_id': '525465a2-3c47-45f1-8528-523b2a4f77b0', 'serving_data': ''}]}

 Using:

url = https://accounts.azuredatabricks.net/api/2.1/accounts/<account_id>/budget-policies

headers = {
'Authorization': f'Bearer <TOKEN>',
'Accept': 'application/json'
}
params = {"filter_by":{"policy_name":"aaaa"}}
response = requests.get(url=url, headers=headers, params=params)

Is this parameter functional?

using as reference: https://docs.databricks.com/api/azure/account/budgetpolicy/list