iex> users=[%{"user" => %{"first_name" => "john", "age" => 23}},
%{"user" => %{"first_name" => "hari", "age" => 22}},
%{"user" => %{"first_name" => "mahesh", "age" => 21}}]
# that is a list of maps
iex> get_in users, [Access.all(), "user", "age"]
[23, 22, 21]
iex> get_in users, [Access.all(), "user", "first_name"]
["john", "hari", "mahesh"]