iex(1)> {:ok, pid} = ABCD.Fourletters.start_link([])
{:ok, #PID<0.350.0>}
iex(2)> ABCD.Fourletters.get(pid)
[]
iex(3)> ABCD.Fourletters.put(pid, "he")
:ok
iex(4)> ABCD.Fourletters.get(pid)
["he"]
iex(5)> ABCD.Fourletters.put(pid, "he")
:ok
iex(6)> ABCD.Fourletters.get(pid)
["he", "he"]
iex(7)> [%{id: :aoeu, start: {ABCD.Fourletters, :start_link, [[]]}}]
[%{id: :aoeu, start: {ABCD.Fourletters, :start_link, [[]]}}]
iex(8)> # iex(2)> {:ok, pid} = Supervisor.start_link(children, strategy: :one_for_one)
nil
iex(9)> children = [%{id: :aoeu, start: {ABCD.Fourletters, :start_link, [[]]}}]
[%{id: :aoeu, start: {ABCD.Fourletters, :start_link, [[]]}}]
iex(10)> {:ok, pid} = Supervisor.start_link(children, strategy: :one_for_one)
{:ok, #PID<0.361.0>}


iex(2)> {:ok, pid} = Supervisor.start_link(children, strategy: :one_for_one)
{:ok, #PID<0.366.0>}
iex(3)> Supervisor.count_children(pid)
%{active: 1, specs: 1, supervisors: 0, workers: 1}
iex(4)> Supervisor.start_child(pid,
...(4)> %{id: :aoeu, start: {ABCD.Fourletters, :start_link, [[]]}})
{:error, {:already_started, #PID<0.367.0>}}
iex(5)> %{id: :tutu, start: {ABCD.Fourletters, :start_link, [[]]}})
** (SyntaxError) iex:5:59: unexpected token: )

iex(5)> Supervisor.start_child(pid, %{id: :tutu, start: {ABCD.Fourletters, :start_link, [[]]}})
{:ok, #PID<0.373.0>}
iex(6)> Supervisor.count_children(pid)
%{active: 2, specs: 2, supervisors: 0, workers: 2}
iex(7)> {:error, {:already_started, child_pid}} = Supervisor.start_child(pid, %{id: :tutu, start: {ABCD.Fourletters, :start_link, [[]]}})
{:error, {:already_started, #PID<0.373.0>}}