code: def combined_rule_prefixes() -> List[str]:
      """Helper function that returns the prefix pattern for the tokenizer.
      It is a helper function to accomodate spacy tests that only test
      prefixes.
      """
      # add lookahead assertions for brackets (may not work properly for unbalanced brackets)
      prefix_punct = char_classes.PUNCT.replace("|", " ")
      prefix_punct = prefix_punct.replace(r"\(", r"\((?![^\(\s]+\)\S+)")
      prefix_punct = prefix_punct.replace(r"\[", r"\[(?![^\[\s]+\]\S+)")
      prefix_punct = prefix_punct.replace(r"\{", r"\{(?![^\{\s]+\}\S+)")
  
      prefixes = (
          ["§", "%", "=", r"\+"]
          + char_classes.split_chars(prefix_punct)
          + char_classes.LIST_ELLIPSES
          + char_classes.LIST_QUOTES
          + char_classes.LIST_CURRENCY
          + char_classes.LIST_ICONS
      )
      return prefixes
  
file_path: scispacy/scispacy/custom_tokenizer.py
imports: from typing import List
  from spacy.lang import char_classes
  from spacy.symbols import ORTH
  from spacy.tokenizer import Tokenizer
  from spacy.util import compile_prefix_regex, compile_infix_regex, compile_suffix_regex
  from spacy.language import Language
  from scispacy.consts import ABBREVIATIONS
label_desc: Use image node_id 2 for calling a global function with example usage: combined_rule_prefixes() and returns: prefixes