dbus_data = {
     sig = <DBus signature>,
     value = <Lua type>
   }

   {
     sig = ldbus.basic_types.int32, -- i.e. "i"
     value = 256
   }

   {
     sig = ldbus.basic_types.boolean, -- i.e. "b"
     value = false
   }

   {
       sig = ldbus.types.variant, -- i.e. "v"
       value = <DBus data>
   }

   {
       sig = ldbus.types.variant,
       value = {
                   sig = ldbus.basic_types.uint32,
                   value = 4294967295
                }
   }

   {
     sig = ldbus.types.array .. <contents signature>,
     value = {<contents>} -- homogeneous array
   }

   {
     sig = "ai", -- i.e. array of int32
     value = {1, 2, 3, 4, 5, 6}
   }
   {
     sig = "aas", -- i.e. array of arrays of strings
     value = {{"a", "b"}, {"c", "d"}, {"e"}}
   }

   {
     sig = ldbus.types.array .. "{" .. <key type> <value type> .. "}",
     value = { <key1> = <value1>, <key2> = <value2>}
   }

   {
     sig = "a{ss}"
     value = {a = "A", b = "B", c = "C"}
   }
   {
     sig = "a{sa{si}}", -- nested dictionary
     value = {outer1 = {inner1 = 1}, outer2 = {inner2 = 2}}
   }

  {
    sig = "(" .. <type1> .. <type2> .. <type3> [...] .. ")",
    value = { <value1>, <value2>, <value3>, [...]} -- heterogeneous array
  }

  {
    sig = "(ibs)",
    value = { 1, true, "hello Lua!"}
  }
  {
    sig = "(ia{si}s)",
    value = {1, {one = 5, two = 6, three = 7}, "hello Lua!"}
  }