尝试执行简单程序时出现类型错误?

嗨,我收到以下代码的TypeError

def fahrenheit(self,T_in_celsius):
""" returns the temperature in degrees Fahrenheit"""
return (T_in_celsius * 9 / 5) + 32

for t in (22.6, 25.8, 27.3, 29.8):
    print(t,":",fahrenheit(t)) 

例外情况:

print(t,":",fahrenheit(t))  
TypeError: fahrenheit() missing 1 required positional argument: 'T_in_celsius'

值在print()中变为t: 22.6 : 25.8 : 27.3 : 29.8 :