问使用fcfg派生sql查询时的NLTK问题

EN

% start S
## Added by me
S[SEM=(?whadvp + ?sq)] -> WHADVP[SEM=?whadvp] SQ[SEM=?sq]

WHADVP[SEM=(?wrb + ?jj)] -> WRB[SEM=?wrb] JJ[SEM=?jj]
SQ[SEM=(?vbp + ?np + ?vp)] -> VBP[SEM=?vbp] NP[SEM=?np] VP[SEM=?vp]
NP[SEM=(?np + ?pp)] -> NP[SEM=?np] PP[SEM=?pp]
NP[SEM=(?np)] -> JJS[SEM=?jjs]
VP[SEM=(?vbz + ?advp)] -> VBZ[SEM=?vbz] ADVP[SEM=?advp]
PP[SEM=(?in + ?np)] -> IN[SEM=?in] NP[SEM=?np]
NP[SEM=(?prp + ?nn)] -> PRP$[SEM=?prp] NN[SEM=?nn]
ADVP[SEM=(?rb)] -> RB[SEM=?rb]

WRB[SEM='SELECT average(calldurationinsexonds) FROM Task'] -> 'How'

JJ[SEM=''] -> 'long'
VBP[SEM=''] -> 'do'
JJS[SEM=''] -> 'most'
IN[SEM=''] -> 'of'
PRP$[SEM=''] -> 'our'
NN[SEM=''] -> 'phone'
VBZ[SEM=''] -> 'calls'
JJ[SEM=''] -> 'last'

## Default example
S[SEM=(?np + WHERE + ?vp)] -> NP[SEM=?np] VP[SEM=?vp]

VP[SEM=(?v + ?pp)] -> IV[SEM=?v] PP[SEM=?pp]
VP[SEM=(?v + ?ap)] -> IV[SEM=?v] AP[SEM=?ap]
NP[SEM=(?det + ?n)] -> Det[SEM=?det] N[SEM=?n]
PP[SEM=(?p + ?np)] -> P[SEM=?p] NP[SEM=?np]
AP[SEM=?pp] -> A[SEM=?a] PP[SEM=?pp]

NP[SEM='Country="greece"'] -> 'Greece'
NP[SEM='Country="china"'] -> 'China'

Det[SEM='SELECT'] -> 'Which' | 'What'

N[SEM='City FROM city_table'] -> 'cities'

IV[SEM=''] -> 'are'
A[SEM=''] -> 'located'
P[SEM=''] -> 'in'

cp = load_parser('grammars/book_grammars/sql0.fcfg')
query = 'How long do most of our phone calls last'
trees = list(cp.parse(query.split()))