code: def find_span(sentence, search_text, start=0):
      search_text = search_text.lower()
      for tok in sentence[start:]:
          remainder = sentence[tok.i :].text.lower()
          if remainder.startswith(search_text):
              len_to_consume = len(search_text)
              start_idx = tok.idx
              for next_tok in sentence[tok.i :]:
                  end_idx = next_tok.idx + len(next_tok.text)
                  if end_idx - start_idx == len_to_consume:
                      span = sentence[tok.i : next_tok.i + 1]
                      return span
      return None
  
file_path: fairseq/examples/roberta/wsc/wsc_utils.py
imports: import json
  from functools import lru_cache
label_desc: Use image node_id 4 for calling a global function with example usage: find_span(sentence, search_text, start) and returns: None, span