docs: def insert(self, revision, index):
          """
          Insert a :class:`revision.data.Revision` at a given index.
  
          :param revision:
          :type revision: :class:`revision.data.Revision`
          :param index:
          :type index: int
          """
          if not isinstance(revision, Revision):
              raise InvalidArgType()
  
          for rev in self.revisions:
              if rev == revision:
                  return self
  
          self.revisions.insert(index, revision)
  
          return self