code: def filter_by_months(self, months):
          
          _filt_values = []
          _filt_datetimes = []
          for i, d in enumerate(self.datetimes):
              if d in months:
                  _filt_datetimes.append(d)
                  _filt_values.append(self._values[i])
          _filt_header = self.header.duplicate()
          return MonthlyCollection(_filt_header, _filt_values, _filt_datetimes)
docs: Filter the Data Collection based on a list of months of the year (as integers).
  
          Args:
             months: A List of months of the year [1..12]
  
          Return:
              A new Data Collection with filtered data