Custom sentence segmentation in Spacy

The following code works:

import spacy
nlp = spacy.load('en_core_web_sm')

def split_on_breaks(doc):
    start = 0
    seen_break = False
    for word in doc:
        if seen_break:
            yield doc[start:word.i-1]
            start = word.i
            seen_break = False
        elif word.text == '@SentBoundary@':
            seen_break = True
    if start < len(doc):
        yield doc[start:len(doc)]

sbd = SentenceSegmenter(nlp.vocab, strategy=split_on_breaks)
nlp.add_pipe(sbd, first=True)

def get_sentences(text):
    doc = nlp(text)
    return (list(doc.sents)) # convert to string if required.

# Ex1
get_sentences("Bob meets Alice. @SentBoundary@ They play together.")
# => ["Bob meets Alice.", "They play together."]  # two sentences

# Ex2
get_sentences("Bob meets Alice. They play together.")
# => ["Bob meets Alice. They play together."]  # ONE sentence

# Ex3
get_sentences("Bob meets Alice, @SentBoundary@ they play together.")
# => ["Bob meets Alice,", "they play together."] # two sentences

Right thing was to check for SentenceSegmenter than manual boundary setting (examples here). This github issue was also helpful.