code: def get_symbol_rets(symbol, start=None, end=None):
      """
      Calls the currently registered 'returns_func'
  
      Parameters
      ----------
      symbol : object
          An identifier for the asset whose return
          series is desired.
          e.g. ticker symbol or database ID
      start : date, optional
          Earliest date to fetch data for.
          Defaults to earliest date available.
      end : date, optional
          Latest date to fetch data for.
          Defaults to latest date available.
  
      Returns
      -------
      pandas.Series
          Returned by the current 'returns_func'
      """
  
      return SETTINGS["returns_func"](symbol, start=start, end=end)
  
imports: from __future__ import division
  import warnings
  from itertools import cycle
  from matplotlib.pyplot import cm
  import numpy
  import pandas
  from IPython.display import display, HTML
  import empyrical.utils
  from .None import pos
  from .None import txn
label_desc: Use image node_id 16 for calling a global function with example usage: get_symbol_rets(symbol, start, end) and returns: SETTINGS