title: Airflow - got an unexpected keyword argument 'conf'
body: <p>I'm learning Apache Airflow to implement it at my workplace,
  I stumbled on a problem, when trying to pass parameter to function like this (I followed the documentation)</p>
  <pre><code>from airflow import DAG
  import pendulum
  from datetime import datetime, timedelta
  from airflow.operators.python_operator import PythonOperator
  
  args = {
      &quot;owner&quot;: &quot;airflow&quot;,
      &quot;start_date&quot;: pendulum.datetime(year=2020, month=10, day=5, tzinfo='Asia/Shanghai'),
      &quot;retries&quot;: 5,
      &quot;retry_delay&quot;: timedelta(minutes=3)
  }
  
  dag = DAG(
      &quot;example_dag_v2&quot;,
      schedule_interval=&quot;@daily&quot;,
      default_args=args
  )
  
  def my_mult_function(number):
      return number*number
  
  mult_task = PythonOperator(
      task_id = 'mult_task',
      provide_context=True,
      python_callable=my_mult_function,
      op_kwargs={'number': 5},
      dag = dag
  )
  
  mult_task
  </code></pre>
  <p>I keep getting this error</p>
  <blockquote>
  <p>TypeError: my_mult_function() got an unexpected keyword argument 'conf'</p>
  </blockquote>
  <p>where did I do wrong ?</p>
  <p>Solution:</p>
  <p>so i found the solution but still dont understand why
  the solution is</p>
  <pre><code>def my_mult_function(number, **kwargs):
      return number*number
  </code></pre>
  <p>i passed **kwargs on the parameters, and it works! But i still dont understand why i need to pass the **kwargs ?</p>