You're seeing just the macro untag-exclamation-mark, go back to Domo.TaggedTuple module for more information.
Link to this macro

untag!(tagged_tuple, tag_chain)

View Source (macro)

Returns the value from the tagged tuple when the tag chain matches.

Raises ArgumentError exception if the passed tag chain is not one that is in the tagged tuple. Supports up to 6 links in the tag chain.


iex> use Domo.TaggedTuple
...> value = {A, {Tag, {Chain, 2}}}
...> untag!(value, {A, {Tag, Chain}})

iex> use Domo.TaggedTuple
...> value = {Other, {Stuff, 2}}
...> untag!(value, {A, {Tag, Chain}})
** (ArgumentError) Tag chain {A, {Tag, Chain}} doesn't match one in the tagged tuple {Other, {Stuff, 2}}.