docstr: Look up the returns for a given dt.
  
  Parameters
  ----------
  dt : datetime
      The label to look up.
  
  Returns
  -------
  returns : float
      The returns at the given dt or session.
  
  See Also
  --------
  :class:`zipline.sources.benchmark_source.BenchmarkSource.daily_returns`
  
  .. warning::
  
     This method expects minute inputs if ``emission_rate == 'minute'``
     and session labels when ``emission_rate == 'daily``.
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code: def get_value(self, dt):
      """Look up the returns for a given dt.
  
      Parameters
      ----------
      dt : datetime
          The label to look up.
  
      Returns
      -------
      returns : float
          The returns at the given dt or session.
  
      See Also
      --------
      :class:`zipline.sources.benchmark_source.BenchmarkSource.daily_returns`
  
      .. warning::
  
         This method expects minute inputs if ``emission_rate == 'minute'``
         and session labels when ``emission_rate == 'daily``.
      """
      return self._precalculated_series.loc[dt]
  
file_path: zipline/zipline/sources/benchmark_source.py
imports: import pandas
  from zipline.errors import InvalidBenchmarkAsset, BenchmarkAssetNotAvailableTooEarly, BenchmarkAssetNotAvailableTooLate
label_desc: Use image node_id 2 for calling the BenchmarkSource obj's underlying member method code with example usage: obj.get_value(dt) and returns: self