code: def _get_attr_by_tag(obj, tag, attr_name):
      
      attr_name = _TAG_ATTR_MODIFIERS[tag] + attr_name
      return getattr(obj, attr_name)
docs: Get attribute from an object via a string tag.
  
      Parameters
      ----------
      obj : object from which to get the attribute
      attr_name : str
          Unmodified name of the attribute to be found.  The actual attribute
          that is returned may be modified be 'tag'.
      tag : str
          Tag specifying how to modify 'attr_name' by pre-pending it with 'tag'.
          Must be a key of the _TAG_ATTR_MODIFIERS dict.
  
      Returns
      -------
      the specified attribute of obj