Do not import any package. python code.

Write a recursive function that takes a base string and a non-empty pattern string, and computes the length of the largest substring of the base that starts and ends with the pattern. If no match is found, return 0. Notes: (1) This function should look for exact matches (case-sensitive). (2) The start pattern and end pattern of the largest substring could fully or partially overlap (see examples below). Examples: base jumpsjump hwhwhw pattern jump output 9 (not overlapped) 5 (partially overlapped) hwh frontsdakonsakdna front 5 (fully overlapped) life life 4 (fully overlapped)