1. Why, if there is an empty cell in the Pandas column, are integer values in this column converted into floats?
2. What is the benefit of plotting missing values?
3. What is regex? Is it a separate language?
4. How can we use regex in Python?

5. How is a regex pattern defined? How can we combine and modify patterns dynamically within the code?
6. Is it a good idea to run ordinary Python functions on dataframe cells? What are the pros and cons of that approach? Should we use loops for that?