code: def _format_range(r):
      return (
          str(pd.Timestamp(r.start, unit="ns")),
          str(pd.Timestamp(r.stop, unit="ns")),
      )
  
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 a global function with example usage: _format_range(r) and returns: str,  str