'Test the _write_auto_filter() method'

def test_write_auto_filter_15(self):

    filter_condition = 'x    >=    4000'
    exp = '<autoFilter    ref="A1:D51"><filterColumn    colId="2"><customFilters><customFilter    operator="greaterThanOrEqual"    val="4000"/></customFilters></filterColumn></autoFilter>'
    self.worksheet.filter_column('C', filter_condition)
    self.worksheet._write_auto_filter()
    got = self.fh.getvalue()
    self.assertEqual(got, exp)
