A document_range is a pair of document_position
objects, with each position indicating the start and end of
the range, respectively.
document_range(start, end = NULL)is.document_range(x)
as.document_range(x)
An list with class document_range and fields:
start: | The start position. | 
end: | The end position. | 
A document_position indicating the start of the
range.
A document_position indicating the end of the
range.
An object coercable to document_range.