For discussions in this course, the following criteria must be used- Your initial post should be a minimum of at least two fully-formed, well-thought-out scholarly paragraphs (blocks of code examples and graphics are considered additional information beyond the two required paragraphs but are encouraged when appropriate).

Describe at least two Pandas library functions that will help you to resolve the data quality issues such as replacing Null values with NaN?

Why is it important to use Pandas library inbuilt functions as compared to writing the user-defined function to improve the data quality?