class_docstr: Preallocation strategies for rolling window over expanding data set
  
  Restrictions: major_axis can only be a DatetimeIndex for now
class_docstr_tok: ["Preallocation","strategies","for","rolling","window","over","expanding","data","set","Restrictions",":","major_axis","can","only","be","a","DatetimeIndex","for","now"]
code: def _create_buffer(self):
      panel = pd.Panel(
          items=self.items,
          minor_axis=self.minor_axis,
          major_axis=range(self.cap),
          dtype=self.dtype,
      )
      return panel
  
imports: import datetime
  from copy import deepcopy
  import numpy
  import pandas
label_desc: Use image node_id 8 for calling the RollingPanel obj's underlying member method code with example usage: obj._create_buffer() and returns: panel