code: def _split(self, x):
      v = []
      if x.ndim == 1:
          for ix in self.stratum_rows:
              v.append(x[ix])
      else:
          for ix in self.stratum_rows:
              v.append(x[ix, :])
      return v
  
imports: import numpy
  from statsmodels.base import model
  import statsmodels.base.model
  from statsmodels.tools.decorators import cache_readonly
  from statsmodels.compat.pandas import Appender
label_desc: Use image node_id 2 for calling the PHSurvivalTime obj's underlying member method code with example usage: obj._split(x) and returns: v