'step4() takes off -ant, -ence etc., in context <c>vcvc<v>.'

def step4(self):

    if (self.b[(self.k - 1)] == 'a'):
        if self.ends('al'):
            pass
        else:
            return
    elif (self.b[(self.k - 1)] == 'c'):
        if self.ends('ance'):
            pass
        elif self.ends('ence'):
            pass
        else:
            return
    elif (self.b[(self.k - 1)] == 'e'):
        if self.ends('er'):
            pass
        else:
            return
    elif (self.b[(self.k - 1)] == 'i'):
        if self.ends('ic'):
            pass
        else:
            return
    elif (self.b[(self.k - 1)] == 'l'):
        if self.ends('able'):
            pass
        elif self.ends('ible'):
            pass
        else:
            return
    elif (self.b[(self.k - 1)] == 'n'):
        if self.ends('ant'):
            pass
        elif self.ends('ement'):
            pass
        elif self.ends('ment'):
            pass
        elif self.ends('ent'):
            pass
        else:
            return
    elif (self.b[(self.k - 1)] == 'o'):
        if (self.ends('ion') and ((self.b[self.j] == 's') or (self.b[self.j] == 't'))):
            pass
        elif self.ends('ou'):
            pass
        else:
            return
    elif (self.b[(self.k - 1)] == 's'):
        if self.ends('ism'):
            pass
        else:
            return
    elif (self.b[(self.k - 1)] == 't'):
        if self.ends('ate'):
            pass
        elif self.ends('iti'):
            pass
        else:
            return
    elif (self.b[(self.k - 1)] == 'u'):
        if self.ends('ous'):
            pass
        else:
            return
    elif (self.b[(self.k - 1)] == 'v'):
        if self.ends('ive'):
            pass
        else:
            return
    elif (self.b[(self.k - 1)] == 'z'):
        if self.ends('ize'):
            pass
        else:
            return
    else:
        return
    if (self.m() > 1):
        self.k = self.j
