Given a 2D binary matrix filled with 0's and 1's, find the largest square containing only 1's and return its area.
Ogige kachasị N'ime nsogbu kachasị, anyị enyela ọnụọgụ ọnụọgụ 2D nke jupụtara na 0 na 1, chọta akụkụ kachasị ibu nwere naanị 1, ma weghachite mpaghara ya.