I am required to type in a regular expression in python in the line that says "pattern $=".$ The code I have typed it is not working. What is the correct regex code?

The grades.txt file I am using is listed here:

Ronald Mayr: A

Bell Kassulke: B

Jacqueline Rupp: A

Alexander Zeller: C

Valentina Denk: C

Simon Loidl: B

Elias Jovanovic: B

Stefanie Weninger: A

Fabian Peer: C

Hakim Botros: B

Emilie Lorentsen: B

Herman Karlsen: C

Nathalie Delacruz: C

Casey Hartman: C

Lily Walker : A

Gerard Wang: C

Tony Mcdowell: C

Jake Wood: B

Fatemeh Akhtar: B

Kim Weston: B

Nicholas Beatty: A

Kirsten Williams: C

Vaishali Surana: C

Coby Mccormack: C

Yasmin Dar: B

Romy Donnelly: A

Viswamitra Upandhye: B

Kendrick Hilpert: A

Killian Kaufman: B

Elwood Page: B

Mukti Patel: A

Emily Lesch: C

Elodie Booker: B

Jedd Kim: A

Annabel Davies: A

Adnan Chen: B

Jonathan Berg: C

Hank Spinka: B

Agnes Schneider: C

Kimberly Green: A

Lola$-$Rose Coates: C

Rose Christiansen: C

Shirley Hintz: C

Hannah Bayer: B