Python 函数头的问题有人了解吗？

def say_hi(name: str, age: int) -> str:
"""
Hi!
"""
# your code here
return "Hi. My name is %s and I'm %d years old" % (name, age)

if __name__ == '__main__':
#These "asserts" using only for self-checking and not necessary for auto-testing
assert say_hi("Alex", 32) == "Hi. My name is Alex and I'm 32 years old", "First"
assert say_hi("Frank", 68) == "Hi. My name is Frank and I'm 68 years old", "Second"
print('Done. Time to Check.')
------------------------------------------------------------------------------
我不太明白 say_hi(name: str, age: int) -> str:这个函数头是什么含义。name: str, age: int 是不是 C 里边的类型声明？-> str:这块完全不理解。

google 能力有限，求各位大佬解答，谢谢。