class_docstr: Class used to write data to an assets db.
  
  Parameters
  ----------
  engine : Engine or str
      An SQLAlchemy engine or path to a SQL database.
class_docstr_tok: ["Class","used","to","write","data","to","an","assets","db",".","Parameters","--","--","--","--","--","engine",":","Engine","or","str","An","SQLAlchemy","engine","or","path","to","a","SQL","database","."]
docstr: Checks if any tables are present in the current assets database.
  
  Parameters
  ----------
  txn : Transaction
      The open transaction to check in.
  
  Returns
  -------
  has_tables : bool
      True if any tables are present, otherwise False.
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code: def _all_tables_present(self, txn):
      """
      Checks if any tables are present in the current assets database.
  
      Parameters
      ----------
      txn : Transaction
          The open transaction to check in.
  
      Returns
      -------
      has_tables : bool
          True if any tables are present, otherwise False.
      """
      conn = txn.connect()
      for table_name in asset_db_table_names:
          if txn.dialect.has_table(conn, table_name):
              return True
      return False
  
imports: from collections import namedtuple
  import re
  import numpy
  import pandas
  import sqlalchemy
  from toolz import first
  from zipline.errors import AssetDBVersionError
  from zipline.assets.asset_db_schema import ASSET_DB_VERSION, asset_db_table_names, asset_router, equities, equity_symbol_mappings, equity_supplementary_mappings, futures_contracts, exchanges, futures_root_symbols, metadata, version_info
  from zipline.utils.compat import ExitStack
  from zipline.utils.preprocess import preprocess
  from zipline.utils.range import from_tuple, intersecting_ranges
  from zipline.utils.sqlite_utils import coerce_string_to_eng
label_desc: Use image node_id 7 for calling the AssetDBWriter obj's underlying member method code with example usage: obj._all_tables_present(txn) and returns: False, True