计算fg文件中染色体的信息，如总长度，有效长度，GC含量，N的长度，以及计算N50和N90.-Calculation chromosome fg file information such as the total length, effective length, GC content, length N, and the calculation of N50 and N90.

以250bp为窗口沿着染色体滑动，计算每个窗口的GC含量。-250bp for the window to slide along the chromosome, calculate GC content of each window.