code: def load_from_directory(list_name):
      """
      To resolve the symbol in the LEVERAGED_ETF list,
      the date on which the symbol was in effect is needed.
  
      Furthermore, to maintain a point in time record of our own maintenance
      of the restricted list, we need a knowledge date. Thus, restricted lists
      are dictionaries of datetime->symbol lists.
      new symbols should be entered as a new knowledge date entry.
  
      This method assumes a directory structure of:
      SECURITY_LISTS_DIR/listname/knowledge_date/lookup_date/add.txt
      SECURITY_LISTS_DIR/listname/knowledge_date/lookup_date/delete.txt
  
      The return value is a dictionary with:
      knowledge_date -> lookup_date ->
         {add: [symbol list], 'delete': [symbol list]}
      """
      data = {}
      dir_path = os.path.join(SECURITY_LISTS_DIR, list_name)
      for kd_name in listdir(dir_path):
          kd = datetime.strptime(kd_name, DATE_FORMAT).replace(
              tzinfo=pytz.utc
          )
          data[kd] = {}
          kd_path = os.path.join(dir_path, kd_name)
          for ld_name in listdir(kd_path):
              ld = datetime.strptime(ld_name, DATE_FORMAT).replace(
                  tzinfo=pytz.utc
              )
              data[kd][ld] = {}
              ld_path = os.path.join(kd_path, ld_name)
              for fname in listdir(ld_path):
                  fpath = os.path.join(ld_path, fname)
                  with open(fpath) as f:
                      symbols = f.read().splitlines()
                      data[kd][ld][fname] = symbols
  
      return data
  
imports: import warnings
  from datetime import datetime
  from os import listdir
  import os.path
  import pandas
  import pytz
  import catalyst
  from catalyst.errors import SymbolNotFound
  from catalyst.finance.asset_restrictions import SecurityListRestrictions
  from catalyst.catalyst_warnings import ZiplineDeprecationWarning
label_desc: Use image node_id 1 for calling a global function with example usage: load_from_directory(list_name) and returns: data