docs: def replace_by_xml(self, xml_str, el_idx=0):
          """Replace element.
  
          Select element that has the same name as ``xml_str``, then replace the selected
          element with ``xml_str``
  
          - ``xml_str`` must have a single element in the root.
          - The root element in ``xml_str`` can have an arbitrary number of children.
  
          Args:
            xml_str : str
              New element that will replace the existing element.
  
          """
          root_el = self.parse_xml(xml_str)
          self.replace_by_etree(root_el, el_idx)