code: def one_child(self, tup_tree, acceptable):
          
  
          k = kids(tup_tree)
  
          if not k:
              raise CIMXMLParseError(
                  _format("Element {0!A} missing required child element {1!A}",
                          name(tup_tree), acceptable),
                  conn_id=self.conn_id)
          if len(k) > 1:
              raise CIMXMLParseError(
                  _format("Element {0!A} has too many child elements {1!A} "
                          "(allowed is one child element {2!A})",
                          name(tup_tree), [name(t) for t in k], acceptable),
                  conn_id=self.conn_id)
  
          child = k[0]
  
          if name(child) not in acceptable:
              raise CIMXMLParseError(
                  _format("Element {0!A} has invalid child element {1!A} "
                          "(allowed is one child element {2!A})",
                          name(tup_tree), name(child), acceptable),
                  conn_id=self.conn_id)
  
          return self.parse_any(child)
docs: Parse children of a node with exactly one child node.
  
          acceptable is a list/tuple of acceptable child nodes
  
          PCData is ignored.