Fix errors in the python project

Given this code: [login to view URL] I want "class FolKB(KB) to be implemented in one file. You can only use python's standard libraries. Non-standard libraries may be included in the same file. Sample test input and output: >>> kb0 = FolKB([expr('Farmer(Mac)'), expr('Rabbit(Pete)'), ... expr('(Rabbit(r) & Farmer(f)) ==> Hates(f, r)')]) >>> [login to view URL](expr('Rabbit(Flopsie)')) >>> [login to view URL](expr('Rabbit(Pete)')) >>> [login to view URL](expr('Hates(Mac, x)'))[x] Flopsie >>> [login to view URL](expr('Wife(Pete, x)')) False