HTML/CSS, JavaScript, Python, and SQL Online Test

Implement the ensure function so that it throws an error if called without arguments or the argument is undefined. Otherwise it should return the given value.

Given the following data definition, write a query that returns the number of students whose first name is John.

TABLE students
   id INTEGER PRIMARY KEY,
   firstName VARCHAR(30) NOT NULL,
   lastName VARCHAR(30) NOT NULL

Update the website's HTML, without using JavaScript or CSS, to make use of semantic elements so that:

• The classless outer div element is replaced with a more appropriate element.
• The divs with the image and caption classes are replaced with self-contained content elements.
• The divs with the lorem-ipsum and description classes are replaced with elements, so that by default only the contents of the description element are shown. When the contents of the description element are clicked, the visibility of the rest of the lorem-ipsum element is toggled.

Implement a group_by_owners function that:

• Accepts a dictionary containing the file owner name for each file name.
• Returns a dictionary containing a list of file names for each owner name, in any order.

For example, for dictionary {'Input.txt': 'Randy', 'Code.py': 'Stan', 'Output.txt': 'Randy'} the group_by_owners function should return {'Randy': ['Input.txt', 'Output.txt'], 'Stan': ['Code.py']}.