如何检查一个列表/字典的元素是否存在于python中的另一个列表/字典中

here is a scenario, I am checking if elements of A are present in B. while this code works, it takes a lot of time when I read through million of lines. The efficient way would be to make each list in A and B as dictionary and look if they are present in each other. But I am not able to think of a simple way to do dictionary lookup. That is for each key-value pair in dict A, I want to check if that key-value pair is present in dictBhere is a scenario, I am checking if elements o