code: def get_symbols_string(assets):
      """
      A concatenated string of symbols from a list of assets.
  
      Parameters
      ----------
      assets: list[TradingPair]
  
      Returns
      -------
      str
  
      """
      array = [assets] if isinstance(assets, TradingPair) else assets
      return ", ".join([asset.symbol for asset in array])
  
imports: import hashlib
  import json
  import os
  import pickle
  import shutil
  from datetime import date, datetime
  import pandas
  from catalyst.assets._assets import TradingPair
  from six import string_types
  from six.moves.urllib import request
  from catalyst.constants import DATE_FORMAT, SYMBOLS_URL
  from catalyst.exchange.exchange_errors import ExchangeSymbolsNotFound
  from catalyst.exchange.utils.serialization_utils import ExchangeJSONEncoder, ExchangeJSONDecoder
  from catalyst.utils.memoize import weak_lru_cache
  from catalyst.utils.paths import data_root, ensure_directory, last_modified_time
label_desc: Use image node_id 9 for calling a global function with example usage: get_symbols_string(assets) and returns: str