code: def bestfit():
      df = cf.datagen.scatter()
      df["x"] = np.random.randint(1, 20, df.shape[0])
      df["y"] = df["x"]
      df = df[["x", "y"]]
  
      options = {
          "kind": ["scatter"],
          "bestfit": [True],
      }
  
      def bestfit(self, **kwargs):
          self._iplot(df, **kwargs)
  
      _generate_tests(TestIPlot, bestfit, "bestfit", options)
  
imports: import cufflinks
  import pandas
  import numpy
  import unittest
  from nose.tools import assert_equals
label_desc: Use image node_id 15 for calling a global function with example usage: bestfit() without return types