@staticmethod
    def _open_file(filename):
        if filename is None:
            raise DataSourceError("Trace filename is not defined")

        try:
            trace_file = open(filename, "r")
        except IOError as e:
            raise DataSourceError("Unable to open trace file %s" % filename, e)
        else:
            LOG.debug("Opened trace file %s", filename)
            return trace_file
Get the start point of the range.  Not a copy, so changing this alters
dataset/ETHPy150Open openxc/openxc-python/openxc/sources/trace.py/TraceDataSource._open_file--crossover with--dataset/ETHPy150Open pyjs/pyjs/pyjswidgets/pyjamas/selection/Range.py/Range.getStartPoint