code: def T(s):
      return pd.Timestamp(s, tz="UTC")
  
imports: from nose_parameterized import parameterized
  import pandas
  from zipline.algorithm import TradingAlgorithm
  import zipline.api
  import zipline.errors
  from zipline.finance.execution import StopLimitOrder
  import zipline.testing.fixtures
  from zipline.testing.predicates import assert_equal
  import zipline.test_algorithms
label_desc: Use image node_id 1 for calling a global function with example usage: T(s) and returns: pd