Ejabberd.Config.Attr.validate

You're seeing just the function validate, go back to Ejabberd.Config.Attr module for more information.
Link to this function

validate(attrs)

Specs

validate([attr()]) :: [{:ok, attr()}] | [{:error, attr(), atom()}]

Takes an attribute or a list of attrs and validate them.

Returns a {:ok, attr} or {:error, attr, cause} for each of the attributes.