'Constructor.
:param tb: The start of the traceback chain to filter.
:param filtered_traceback: The first traceback of a trailing
chain that is to be filtered.'

def __init__(self, tb, filtered_traceback):

    self._tb = tb
    self.tb_lasti = self._tb.tb_lasti
    self.tb_lineno = self._tb.tb_lineno
    self.tb_frame = self._tb.tb_frame
    self._filtered_traceback = filtered_traceback
