docs: def location(self, filetype, base_dir=None, **kwargs):
          """Return the location of the relative sas path of a given type of file.
  
          Parameters
          ----------
          filetype : str
              File type parameter.
  
          Returns
          -------
          full : str
              The relative sas path to the file.
          """
  
          full = kwargs.get('full', None)
          if not full:
              full = self.full(filetype, **kwargs)
  
          self.set_base_dir(base_dir=base_dir)
          location = full[len(self.base_dir):] if full and full.startswith(self.base_dir) else None
  
          if location and '//' in location:
              location = location.replace('//', '/')
  
          return location