I have tried to execute above code , it executing first def get_invoice_amount when comes second get_invoice_approver it’s showing below error

Traceback (most recent call last):
  File "invoice_approval_skk.py", line 145, in <module>
    worker.run()
  File "/home/applmgr/santhoshk/camundaWorker.py", line 97, in run
    return_variables = self.topic_funcs[task.topic_name](**task.variables)

Below is python code and to process the flow and if i missed anything let me know

def get_invoice_amount(amount: pycamunda.variable.Variable) -> typing.Dict:
    try:
        print('in find inv amount input - ' + str(column2_value))
        invoice_amount = column2_value
    except (AttributeError, ValueError) as e:
        raise worker.ExternalTaskException(message=f'Invalid input: {e}')

    return {'amount': invoice_amount}
def get_invoice_approver(amount: pycamunda.variable.Variable , approver: pycamunda.variable.Variable) -> typing.Dict[int , str]:
    print('in Getting invoice approver:')
    return {'approver': str(column1_value)}


if __name__ == '__main__':
    import pycamunda.processdef

    print('Starting the process')

    url = 'http://localhost:8080/engine-rest't'
    worker_id = '3'

    start_instance = pycamunda.processdef.StartInstance(url=url, key='Invoice_skk2')
    print(column2_value)
    start_instance.add_variable(name='invoice_id', value=1)
    start_instance.add_variable(name='amount', value=column2_value)
    start_instance.add_variable(name='approver', value=column1_value)
   #start_instance.add_variable(name='attachment_file', value=None)
    print('In Mail')
    start_instance()

    worker = worker.Worker(url=url, worker_id=worker_id)
    print('getInvoiceAmountTopic')
    worker.subscribe(
        topic='getInvoiceAmountTopic',
        func=get_invoice_amount,
        variables=['amount']
    )
    
    print('getInvoiceApproverTopic')
    worker.subscribe(
        topic='getInvoiceApproverTopic',
        func=get_invoice_approver,
        variables=['amount','approver']
    )

    worker.run()