docs: def next_conkey(self, conkey):
          """Return the next <conkey><n> based on conkey as a
          string. Example, if 'startcond3' and 'startcond5' exist, this
          will return 'startcond6' if 'startcond5' value is not None,
          else startcond5 is returned.
  
          It is assumed conkey is a valid condition key.
  
          .. warning::
             Under construction. There is work to do. This function in
             combination with the pack.add_condition. But now it's time for
             bed.
  
          """
  
          if conkey in self.conditions:
              return conkey       # Explicit conkey
  
          conkeys = self.sorted_conkeys(prefix=conkey)  # Might be empty.
          if not conkeys:
              # A trailing number given that does not already exist.
              # accept possible gap from previous number.
              return conkey
          for candidate in conkeys:
              if self.conditions[candidate] is None:
                  return candidate
  
          i = self.cond_int(candidate)  # The last one.
          return re.sub(r'\d+', str(i + 1), candidate)