Returns an object of class c("tbl_df", "tbl", "data.frame")
containing one row for every document in the corpus.
The returned data frame includes at least the following columns:
"id" - integer. Id of the source document.
"time" - date time. The time at which the parser was run on
the text.
"version" - character. Version of the CoreNLP library used
to parse the text.
"language" - character. Language of the text, in ISO 639-1
format.
"uri" - character. Description of the raw text location.
Set to NA
if parsed from in-memory character
vector.
Other application specific columns may be included as additional
variables.