docs: def addrs2managers(addrs):
      '''Map agent addresses to their assumed managers.
  
      .. seealso::
  
          :func:`creamas.util.get_manager`
      '''
      mgrs = {}
      for addr in addrs:
          mgr_addr = get_manager(addr)
          if mgr_addr not in mgrs:
              mgrs[mgr_addr] = []
          mgrs[mgr_addr].append(addr)
      return mgrs