code: def verify_dependencies(self):
          
  
          for i in range(1, len(self.deps)):
              assert(not (isinstance(self.deps[i], Transformation) and
                     isinstance(self.deps[i - 1], Analysis))
                     ), "invalid dep order for %s" % self
docs: Checks no analysis are called before a transformation,
          as the transformation could invalidate the analysis.