code: def test_prophet_copy_custom(self, data, backend):
      changepoints = pd.date_range("2012-06-15", "2012-09-15")
      cutoff = pd.Timestamp("2012-07-25")
      m1 = Prophet(changepoints=changepoints, stan_backend=backend)
      m1.add_seasonality("custom", 10, 5)
      m1.add_regressor("binary_feature")
      m1.fit(data)
      m2 = diagnostics.prophet_copy(m1, cutoff=cutoff)
      changepoints = changepoints[changepoints < cutoff]
      assert (changepoints == m2.changepoints).all()
      assert "custom" in m2.seasonalities
      assert "binary_feature" in m2.extra_regressors
  
imports: import datetime
  import itertools
  import numpy
  import pandas
  import pytest
  from prophet import Prophet, diagnostics
label_desc: Use image node_id 3 for calling the TestProphetCopy obj's underlying member method code with example usage: obj.test_prophet_copy_custom(data, backend) without return types