[Bug]: Sentence Splitters do not set previous and next sentence

[alanakbik]

Describe the bug

The Sentence object has .previous_sentence() and .next_sentence() methods to point to the previous and next sentence in the same document respectively. However, our sentence splitters currently do not set these fields.

To Reproduce

from flair.splitter import SegtokSentenceSplitter

text = "This is a text. I am happy."

splitter = SegtokSentenceSplitter()

sentences = splitter.split(text)

for sentence in sentences:
    print("--")
    print(sentence)
    print(sentence.previous_sentence())
    print(sentence.next_sentence())

Expected behavior

The printouts for previous and next sentence should be set where appropriate.

Logs and Stack traces

No response

Screenshots

No response

Additional Context

No response

Environment

Versions:

Flair

0.13.1

Pytorch

2.0.0+cu117

Transformers

4.31.0

GPU

False

[alanakbik]

Closed by #3397