docs: def get_attr_value(self, attr_key, el_idx=0):
          """Return the value of the selected attribute in the selected element.
  
          Args:
            attr_key : str
              Name of attribute for which to search
  
            el_idx : int
              Index of element to use in the event that there are multiple sibling
              elements with the same name.
  
          Returns:
            str : Value of the selected attribute in the selected element.
  
          """
          return self.get_element_by_attr_key(attr_key, el_idx).attrib[attr_key]