code: def str_strip(arr, to_strip=None, side='both'):
      
      if side == 'both':
          f = lambda x: x.strip(to_strip)
      elif side == 'left':
          f = lambda x: x.lstrip(to_strip)
      elif side == 'right':
          f = lambda x: x.rstrip(to_strip)
      else:  # pragma: no cover
          raise ValueError('Invalid side')
      return _na_map(f, arr)
docs: Strip whitespace (including newlines) from each string in the
      Series/Index.
  
      Parameters
      ----------
      to_strip : str or unicode
      side : {'left', 'right', 'both'}, default 'both'
  
      Returns
      -------
      Series or Index