How to use the @paypal/sdk-constants.FUNDING.PAYPAL function in @paypal/sdk-constants

function getFundingEligibilityParam(req : ExpressRequest) : FundingEligibility {
    const encodedFundingEligibility = req.query.fundingEligibility;

    if (encodedFundingEligibility && typeof encodedFundingEligibility === 'string') {
        return JSON.parse(
            Buffer.from(encodedFundingEligibility, 'base64').toString('utf8')
        );
    }

    // $FlowFixMe
    return {
        [ FUNDING.PAYPAL ]: {
            eligible: true
        }
    };
}

export async function clickButton(fundingSource? : string = FUNDING.PAYPAL, card? : string = CARD.VISA) : ZalgoPromise {
    let selector = `button[data-funding-source=${ fundingSource }]`;
    if (fundingSource === FUNDING.CARD) {
        selector = `${ selector }[data-card=${ card }]`;
    }
    const button = window.document.querySelector(selector);
    button.click();
    await button.payPromise;
}

export function enterButton(fundingSource? : string = FUNDING.PAYPAL) {
    triggerKeyPress(window.document.querySelector(`button[data-funding-source=${ fundingSource }]`), 13);
}

export const DEFAULT_FUNDING_ELIGIBILITY = {
    [ FUNDING.PAYPAL ]: {
        eligible: true
    }
};

export function createButtonHTML(fundingEligibility? : Object = DEFAULT_FUNDING_ELIGIBILITY) {
    const buttons = [];
    
    for (const fundingSource of values(FUNDING)) {
        const fundingConfig = fundingEligibility[fundingSource];

        if (!fundingConfig || !fundingConfig.eligible) {
            continue;
        }

        buttons.push(`<button data-funding-source="${ fundingSource }">`);
</button>

return await wrapPromise(async ({ expect }) => {
            const fundingSource = FUNDING.PAYPAL;

            mockFunction(window.paypal, 'Checkout', expect('Checkout', ({ args: [ props ] }) => {
                if (props.fundingSource !== fundingSource) {
                    throw new Error(`Expected fundingSource to be ${ fundingSource }, got ${ props.fundingSource }`);
                }

                return {
                    renderTo: promiseNoop
                };
            }));

            createButtonHTML();

            await mockSetupButton({ merchantID: [ 'XYZ12345' ], fundingEligibility: DEFAULT_FUNDING_ELIGIBILITY });

            await clickButton(fundingSource);

eligible:           types.boolean,
            vaultable:          types.boolean,
            vaultedInstruments: getVaultedInstrumentQuery()
        };
    };

    const getCardQuery = () => {
        return {
            eligible: types.boolean,
            branded:  types.boolean,
            vendors:  getVendorQuery()
        };
    };

    const fundingQuery = {
        [ FUNDING.PAYPAL ]:     getPayPalQuery(),
        [ FUNDING.CARD ]:       getCardQuery(),
        [ FUNDING.VENMO ]:      getBasicFundingEligibilityQuery(),
        [ FUNDING.ITAU ]:       getBasicFundingEligibilityQuery(),
        [ FUNDING.CREDIT ]:     getBasicFundingEligibilityQuery(),
        [ FUNDING.SEPA ]:       getBasicFundingEligibilityQuery(),
        [ FUNDING.IDEAL ]:      getBasicFundingEligibilityQuery(),
        [ FUNDING.BANCONTACT ]: getBasicFundingEligibilityQuery(),
        [ FUNDING.GIROPAY ]:    getBasicFundingEligibilityQuery(),
        [ FUNDING.EPS ]:        getBasicFundingEligibilityQuery(),
        [ FUNDING.SOFORT ]:     getBasicFundingEligibilityQuery(),
        [ FUNDING.MYBANK ]:     getBasicFundingEligibilityQuery(),
        [ FUNDING.P24 ]:        getBasicFundingEligibilityQuery(),
        [ FUNDING.ZIMPLER ]:    getBasicFundingEligibilityQuery(),
        [ FUNDING.WECHATPAY ]:  getBasicFundingEligibilityQuery(),
        [ FUNDING.PAYU ]:       getBasicFundingEligibilityQuery(),
        [ FUNDING.BLIK ]:       getBasicFundingEligibilityQuery(),