How do I resolve TypeError: transactionContract.publishTransaction is not a function

Question

I am trying to write a code to save my transactions on sanity database, but I keep getting TypeError: transactionContract.publishTransaction is not a function. How do I fit it?

import React, { useState, useEffect } from 'react'
import { contractABI, contractAddress } from '../lib/constants'
import { ethers } from 'ethers'
import { client } from '../lib/sanityClient'

export const TransactionContext = React.createContext()

let eth

if (typeof window !== 'undefined') {
    eth = window.ethereum
}

const getEthereumContract = () => {
    const provider = new ethers.providers.Web3Provider(eth)
    const signer = provider.getSigner()
    const transactionContract = new ethers.Contract(
        contractAddress,
        contractABI,
        signer
    )

    return transactionContract
}

export const TransactionProvider = ({ children }) => {
    const [currentAccount, setCurrentAccount] = useState()
    const [isLoading, setIsLoading] = useState(false)
    const [formData, setFormData] = useState({
        addressTo: '',
        amount: '',
    })

useEffect(() => {
    checkIfWalletIsConnected()
}, [])

const connectWallet = async (metamask = eth) => {
    try {
        if (!metamask) return alert('Please install metamask')
        const accounts = await metamask.request({ method: 'eth_requestAccounts' })
        setCurrentAccount(accounts[0])
    } catch (error) {
        console.log(error)
        throw new Error('No ethereum object.')
    }
}

const checkIfWalletIsConnected = async (metamask = eth) => {
    try {
        if (!metamask) return alert('Please install metamask')

        const accounts = await metamask.request({ method: 'eth_accounts' })

        if (accounts.length) {
            setCurrentAccount(accounts[0])
            console.log('Wallet is already connected')
        }
    } catch (error) {
        console.error(error)
        throw new Error('No ethereum object.')
    }
}

const sendTransaction = async (
    metamask = eth,
    connectedAccount = currentAccount
) => {
    try {
        if (!metamask) return alert('Please, install metamask.')
        const { addressTo, amount } = formData
        const transactionContract = getEthereumContract()

        const parsedAmount = ethers.utils.parseEther(amount)

        await metamask.request({
            method: 'eth_sendTransaction',
            params: [
                {
                    from: connectedAccount,
                    to: addressTo,
                    gas: '0x7EF40', // 520000 Gwei
                    value: parsedAmount._hex,
                },
            ],
        })
        
        const transactionHash = await transactionContract.publishTransaction(
            addressTo,
            parsedAmount,
            `Transferring ETH ${parsedAmount} to ${addressTo}`,
            'TRANSFER'
        )

        setIsLoading(true)

        await transactionHash.wait()

        // DB
        await saveTransaction(
            transactionHash.hash,
            amount,
            connectedAccount,
            addressTo
        )

        setIsLoading(false)
    } catch (error) {
        console.log(error)
    }
}

const handleChange = (e, name) => {
    setFormData((prevState) => ({ ...prevState, [name]: e.target.value }))
}

const saveTransaction = async (
    txHash,
    amount,
    fromAddress = currentAccount,
    toAddress
) => {
    const txDoc = {
        _type: 'transactions',
        _id: txHash,
        fromAddress: fromAddress,
        toAddress: toAddress,
        timestamp: new Date(Date.now()).toISOString(),
        txHash: txHash,
        amount: parseFloat(amount),
    }

    await client.createIfNotExists(txDoc)

    await client
        .patch(currentAccount)
        .setIfMissing({ transactions: [] })
        .insert('after', 'transactions[-1]', [
            {
                _key: txHash,
                _ref: txHash,
                _type: 'reference',
            },
        ])
        .commit()

    return
}

return (
    <TransactionContext.Provider
        value={{
            currentAccount,
            connectWallet,
            sendTransaction,
            handleChange,
            formData,
        }}
    >
        {children}
    </TransactionContext.Provider>
)
}

This is the full file. I can't understand why transactionContract.publishTransaction is not a function.

what do I need to do or change?