fix python write example, offset of array was wrong
fix python write example, offset of array was wrong

ornladios/ADIOS2,ornladios/ADIOS2,ornladios/ADIOS2,JasonRuonanWang/ADIOS2,ornladios/ADIOS2,ornladios/ADIOS2,JasonRuonanWang/ADIOS2,JasonRuonanWang/ADIOS2,JasonRuonanWang/ADIOS2,JasonRuonanWang/ADIOS2