Essence.Document.context_of

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

context_of(doc, token, n \\ 5)

Specs

context_of(
  doc :: %Essence.Document{
    meta: term(),
    nested_tokens: term(),
    text: term(),
    type: term(),
    uri: term()
  },
  token :: String.t(),
  n :: number()
) :: List.t()

For each occurrence of token in the given Essence.Document, doc, returns a list containing the token as well as n (default=5) tokens to the left and right of the occurrence.