docs: def add_replace(self, selector, replacement, upsert=False,
                      collation=None):
          """Create a replace document and add it to the list of ops.
          """
          validate_ok_for_replace(replacement)
          cmd = SON([('q', selector), ('u', replacement),
                     ('multi', False), ('upsert', upsert)])
          collation = validate_collation_or_none(collation)
          if collation is not None:
              self.uses_collation = True
              cmd['collation'] = collation
          self.ops.append((_UPDATE, cmd))