code: def set(self, child, min_occurs=1, max_occurs=1):
          
          if isinstance(child, LeafSchema):
              raise RuntimeError("Sequence can't have leaf children")
          if self.child is not None:
              raise RuntimeError("Sequence has already a child")
          if min_occurs is None or max_occurs is None:
              raise RuntimeError("Sequence node without min or max")
          if isinstance(child, LeafSchema):
              raise RuntimeError("Sequence node with leaf child type")
          if not child.tag == "item":
              raise RuntimeError("Sequence node with bad child tag")
  
          self.child = child
          self.min_occurs = min_occurs
          self.max_occurs = max_occurs
          return child
docs: Set the schema for the sequence children.
  
          @param child: The schema that children must match.
          @param min_occurs: The minimum number of children the sequence
              must have.
          @param max_occurs: The maximum number of children the sequence
              can have.