Dealing with fees in smart contracts

General
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4

I have been looking through on how to get one transaction to pay for all fees of all transactions and can’t seem to find an example online.


params = algod_client.suggested_params()
    # comment out the next two (2) lines to use suggested fees
    params.flat_fee = True
    params.fee = 1000

	# create transactions
    print("Creating transactions...")
	# from account 1 to account 3
    sender = account_1
    receiver = account_3
    amount = 1000000
    txn_1 = transaction.PaymentTxn(sender, params, receiver, amount)
    print("...txn_1: from {} to {} for {} microAlgos".format(sender, receiver, amount))
    print("...created txn_1: ", txn_1.get_txid())

	# from account 2 to account 1
    sender = account_2
    receiver = account_1
    amount = 2000000
    txn_2 = transaction.PaymentTxn(sender, params, receiver, amount)
    print("...txn_2: from {} to {} for {} microAlgos".format(sender, receiver, amount))
    print("...created txn_2: ", txn_2.get_txid())

	# combine transations
    print("Combining transactions...")
	# the SDK does this implicitly within grouping below
     
    print("Grouping transactions...")
	# compute group id and put it into each transaction
    group_id = transaction.calculate_group_id([txn_1, txn_2])
    print("...computed groupId: ", group_id)
    txn_1.group = group_id
    txn_2.group = group_id

	# split transaction group
    print("Splitting unsigned transaction group...")
    # this example does not use files on disk, so splitting is implicit above

	# sign transactions
    print("Signing transactions...")
    stxn_1 = txn_1.sign(sk_1)    
    print("...account1 signed txn_1: ", stxn_1.get_txid())
    stxn_2 = txn_2.sign(sk_2)
    print("...account2 signed txn_2: ", stxn_2.get_txid())

	# assemble transaction group
    print("Assembling transaction group...")
    signed_group =  [stxn_1, stxn_2]

	# send transactions
    print("Sending transaction group...")
    tx_id = algod_client.send_transactions(signed_group)

In the example code above, how would I get txn_1 to pay for all the fees?

Also, if the second transaction was an application inner transaction (hypothetically), would I need to write Teal code to have the fees payed by txn_1?