UnboundLocalError: cannot access local variable の原因と直し方

 1  total = 100
 2  
 3  def add_tax():
 4      ______________
               ^
 5      total = total * 1.1
 6      return total
 7  
 8  print(add_tax())

Traceback (most recent call last): File "main.py", line 8, in <module> print(add_tax()) ^^^^^^^^^ File "main.py", line 5, in add_tax total = total * 1.1 ^^^^^ UnboundLocalError: cannot access local variable 'total' where it is not associated with a value