docs: def get_element_by_attr_key(self, attr_key, el_idx=0):
          """
      Args:
        attr_key : str
          Name of attribute for which to search
  
        el_idx : int
          Index of element to use as base in the event that there are multiple sibling
          elements with the same name.
  
      Returns:
        Element containing an attribute key named ``attr_key``.
      """
          el_list = self.get_element_list_by_attr_key(attr_key)
          try:
              return el_list[el_idx]
          except IndexError:
              raise SimpleXMLWrapperException(
                  'Element with tag not found. tag_name="{}" requested_idx={} '
                  'available_elements={}'.format(attr_key, el_idx, len(el_list))
              )