Not able to disable the notifications in budget

[abhi27]

I want to disable notifications that triggers based on threshold rules defined. I tried it using the Post API but getting 400 error.
API url:  https://billingbudgets.googleapis.com/v1/billingAccounts/{billing_id}/budgets

request body: 

request_body = {

        "displayName": "test-budget",

        "budgetFilter": {

            "projects": [

                "projects/{project_id}"

            ],

            "calendar_period": "QUARTER"

        },

        "amount": {

            "specifiedAmount": {

                "units": 10

            }

        },

        "thresholdRules": {

            "thresholdPercent": 0.8,

            "spendBasis": "CURRENT_SPEND"

        },

        "notificationsRule": {

            "pubsubTopic": "projects/ceq-gcp-finops/topics/test-budget",

            "monitoringNotificationChannels": [

                "testchannel"

            ],

        "disableDefaultIamRecipients": True,

        "enableProjectLevelRecipients": False

        }

    }