withColumn, filter and when methods are commonly used to add, modify, or filter columns in a DataFrame. When
long or complex expressions are directly passed to those functions, it can lead to code that is difficult to read, understand, and maintain.
Refactoring such expressions into functions or variables will help with readability. Also, it will become easier to write unit tests for these
functions, ensuring that the logic is correct and behaves as expected. This leads to more robust and reliable code.
