code: def next(self):
      c, p = scipy.stats.pearsonr(
          self.data0.get(size=self.p.period),
          self.data1.get(size=self.p.period),
      )
  
      self.lines.correlation[0] = c
  
file_path: backtrader/samples/gold-vs-sp500/gold-vs-sp500.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import argparse
  import datetime
  import scipy.stats
  import backtrader
label_desc: Use image node_id 1 for calling the PearsonR obj's underlying member method code with example usage: obj.next() without return types