code: def mock_ner_span(text, tag, start, end):
      span = Span([]).set_label("class", tag)
      span.start_pos = start
      span.end_pos = end
      span.tokens = [Token(text[start:end])]
      return span
  
file_path: flair/tests/test_visual.py
imports: from flair.data import Sentence, Span, Token
  from flair.embeddings import FlairEmbeddings
  from flair.visual import Highlighter
  from flair.visual.ner_html import HTML_PAGE, PARAGRAPH, TAGGED_ENTITY, render_ner_html
  from flair.visual.training_curves import Plotter
label_desc: Use image node_id 3 for calling a global function with example usage: mock_ner_span(text, tag, start, end) and returns: span