docs: def check_dependency(self, operation, dependency):
          """
          Enhances default behavior of method by checking dependency for matching operation.
          """
          if isinstance(dependency[1], SQLBlob):
              # NOTE: we follow the sort order created by `assemble_changes` so we build a fixed chain
              # of operations. thus we should match exact operation here.
              return dependency[3] == operation
          return super(MigrationAutodetector, self).check_dependency(operation, dependency)