'Returns the previous tabstop before \'number\'.'

def _get_prev_tab(self, number):

    if (not len(self._tabstops.keys())):
        return
    tno_min = min(self._tabstops.keys())
    possible_sol = []
    i = (number - 1)
    while ((i >= tno_min) and (i > 0)):
        if (i in self._tabstops):
            possible_sol.append((i, self._tabstops[i]))
            break
        i -= 1
    child = [c._get_prev_tab(number) for c in self._editable_children]
    child = [c for c in child if c]
    possible_sol += child
    if (not len(possible_sol)):
        return None
    return max(possible_sol)
