docs: def is_cidr_in_cidr(small_cidr, big_cidr):
      """
      Return True if the small CIDR is contained in the big CIDR.
  
      """
      # The default route (0.0.0.0/0) is handled differently, since every route
      # would always be contained in there. Instead, only a small CIDR of
      # "0.0.0.0/0" can match against it. Other small CIDRs will always result in
      # 'False' (not contained).
      if small_cidr == "0.0.0.0/0":
          return big_cidr == "0.0.0.0/0"
      else:
          if big_cidr == "0.0.0.0/0":
              return False
  
      s = ipaddress.IPv4Network(unicode(small_cidr))
      b = ipaddress.IPv4Network(unicode(big_cidr))
      return s.subnet_of(b)