0PAX Example 7.4.10. The left (respectively second) side of the diagram below shows a typical instance where the left (respectively right) sum of Lemma 7.4.9 is nonzero.
![[Uncaptioned image]](/assets/author-raster/W000055/1034a4d0b24cfcf80a321b8f73cc66a209b95fb51dde73b439df8d3bd8c5c2f5.png)