python顺序查找函数输出问题

def linear_search(data_set,value):
    for i in range(len(data_set)):
        if data_set[i] == value:
    return i
    else:
    return none

a = [1,2,3]
b = 0
linear_search(a,b)

IndentationError: expected an indented block
这个问题怎么解决

def linear_search(data_set,value):
    for i in range(len(data_set)):
        if data_set[i] == value:
            return i
    else:
        return None

a = [1,2,3]
b = 1
x = linear_search(a,b)

print(x)

return none 需要缩进

 
def linear_search(data_set,value):
    for i in range(len(data_set)):
        if data_set[i] == value:
          return i
    else:
      return None
a = [1,2,3]
b = 0
linear_search(a,b)