code: def time_str(self, freq):
      str(self.per)
  
imports: import numpy
  from pandas._libs.tslibs.period import Period, periodarr_to_dt64arr
  from pandas.tseries.frequencies import to_offset
  from .tslib import _sizes, _tzs, tzlocal_obj
label_desc: Use image node_id 5 for calling the PeriodUnaryMethods obj's underlying member method code with example usage: obj.time_str(freq) without return types