'Inflects the verb and returns the given tense (or None).
For example: be
- Verbs.conjugate("is", INFINITVE) => be
- Verbs.conjugate("be", PRESENT, 1, SINGULAR) => I am
- Verbs.conjugate("be", PRESENT, 1, PLURAL) => we are
- Verbs.conjugate("be", PAST, 3, SINGULAR) => he was
- Verbs.conjugate("be", PAST, aspect=PROGRESSIVE) => been
- Verbs.conjugate("be", PAST, person=1, negated=True) => I wasn\'t'

def conjugate(self, verb, *args, **kwargs):

    id = tense_id(*args, **kwargs)
    i1 = self._format.get(id)
    i2 = self._format.get(self._default.get(id))
    i3 = self._format.get(self._default.get(self._default.get(id)))
    b = self.lemma(verb, parse=kwargs.get('parse', True))
    v = []
    if (b in self):
        v = self[b]
        for i in (i1, i2, i3):
            if ((i is not None) and (0 <= i < len(v)) and v[i]):
                return v[i]
    if (kwargs.get('parse', True) is True):
        v = self.find_lexeme(b)
        for i in (i1, i2, i3):
            if ((i is not None) and (0 <= i < len(v)) and v[i]):
                return v[i]
