Keyword.keys
You're seeing just the function
keys, go back to Keyword module for more information.
Specs
Returns all keys from the keyword list.
Duplicated keys appear duplicated in the final list of keys.
Examples
iex> Keyword.keys(a: 1, b: 2)
[:a, :b]
iex> Keyword.keys(a: 1, b: 2, a: 3)
[:a, :b, :a]
iex> Keyword.keys([{:a, 1}, {"b", 2}, {:c, 3}])
** (ArgumentError) expected a keyword list, but an entry in the list is not a two-element tuple with an atom as its first element, got: {"b", 2}