fst：有限状态传感器
佐贺贤治
用法
import fst
# Encode a string as an FST, using white space as separator
myfst1 = fst . linear_chain_from_string ( "This is a test" , ' ' )
# Create an FST transition by transition
myfst2 = fst . FST ()
myfst2 . add_transition ( 'w0
