Essence.Vocabulary.top_tokens

You're seeing just the function top_tokens, go back to Essence.Vocabulary module for more information.
Link to this function

top_tokens(doc, filter_fun \\ &always_true/1)

Return a list of {int, token} pairs, ordered by their token frequency in the given Essence.Document. Optionally supply a filter function such as Essence.Token.is_word?/1 to exclude unwanted tokens from the calculation.