Question $1(20$ marks$)$You should be able to answer this question after you have studied up to Chapter $13$ where Big$-$Oh notation is introduced, though probably you will be able to attempt most of it after studying Chapter $4$ on Sequences and iteration.This question assesses the learning outcomes: Develop and apply algorithms and data structures to solve computational problems. Analyse the complexity of algorithms to support software design choices. Explain how an algorithm or data structure works in order to communicate with relevant stakeholders. Write readable, tested, documented and efficient Python code.We wish to develop a function to return the longest common substring of two character strings, which we will call left and right. We will use examples representing DNA sequences, so the strings we use will only contain the characters $\text{'}$A$\text{'},\text{'}$C$\text{'},\text{'}$G$\text{'},\text{'}$T$\text{'},$ but the function should work for any valld character string.In this question, we want you to take a brute force $($exhaustive search$)$ approach but to build up the function in stages as outlined below.Q$1($a$)(3$ marks$)$Write and test a Python function common$\_$pair, that checks whether any two consecutive characters of left match any two consecutive characters in