code: def identify_degenerate_nests(nest_spec):
      
      degenerate_positions = []
      for pos, key in enumerate(nest_spec):
          if len(nest_spec[key]) == 1:
              degenerate_positions.append(pos)
      return degenerate_positions
docs: Identify the nests within nest_spec that are degenerate, i.e. those nests
      with only a single alternative within the nest.
  
      Parameters
      ----------
      nest_spec : OrderedDict.
          Keys are strings that define the name of the nests. Values are lists
          of alternative ids, denoting which alternatives belong to which nests.
          Each alternative id must only be associated with a single nest!
  
      Returns
      -------
      list.
          Will contain the positions in the list of keys from `nest_spec` that
          are degenerate.