IO.ANSI.format
You're seeing just the function
format, go back to IO.ANSI module for more information.
Formats a chardata-like argument by converting named ANSI sequences into actual ANSI codes.
The named sequences are represented by atoms.
It will also append an IO.ANSI.reset/0 to the chardata when a conversion is
performed. If you don't want this behaviour, use format_fragment/2.
An optional boolean parameter can be passed to enable or disable
emitting actual ANSI codes. When false, no ANSI codes will be emitted.
By default checks if ANSI is enabled using the enabled?/0 function.
Examples
iex> IO.ANSI.format(["Hello, ", :red, :bright, "world!"], true)
[[[[[[], "Hello, "] | "\e[31m"] | "\e[1m"], "world!"] | "\e[0m"]