title: How to get input symbols from a fst model using the OpenFST python extension?
body: <p>OpenFST provides a <a href="http://www.openfst.org/twiki/bin/view/FST/PythonExtension" rel="nofollow">python extension</a>. Is ist possible to read input symbols (isyms) from a compiled FST model using that API?</p>
  
  <p>I can't find the right property or method to do that:</p>
  
  <pre><code>&gt;&gt;&gt; import fst
  &gt;&gt;&gt; f = fst.Fst('/home/jan/Downloads/en_us_nostress/model.fst')
  &gt;&gt;&gt; dir(f)
  ['__class__', '__delattr__', '__doc__', '__format__',
  '__getattribute__', '__hash__', '__init__', '__new__', '__reduce__',
  '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__',
  '__subclasshook__', '_arc_type', '_check_mutating_imethod',
  '_fst_type', '_weight_type', 'arcsort', 'closure', 'concat',
  'connect', 'decode', 'encode', 'invert', 'minimize', 'project',
  'properties', 'prune', 'push', 'relabel', 'reweight', 'rmepsilon',
  'topsort', 'union', 'verify', 'write']
  &gt;&gt;&gt; dir(fst)
  ['ACCEPTOR','ACCESSIBLE', 'ACYCLIC', 'ADD_ARC_PROPERTIES',
  'ADD_STATE_PROPERTIES', 'ADD_SUPERFINAL_PROPERTIES', 
  'ARC_SORT_PROPERTIES', 'BINARY_PROPERTIES', 'COACCESSIBLE',
  'COPY_PROPERTIES', 'CYCLIC', 'DELETE_ARC_PROPERTIES', 
  'DELETE_STATE_PROPERTIES', 'EPSILONS', 'ERROR', 'EXPANDED', 
  'EXTRINSIC_PROPERTIES', 'FST_PROPERTIES', 'Fst',
  'FstError', 'FstWarning', 'INITIAL_ACYCLIC', 'INITIAL_CYCLIC',
  'INTRINSIC_PROPERTIES', 'I_DETERMINISTIC', 'I_EPSILONS',
  'I_LABEL_INVARIANT_PROPERTIES', 'I_LABEL_SORTED', 'MUTABLE',
  'NEG_TRINARY_PROPERTIES', 'NON_I_DETERMINISTIC',
  'NON_O_DETERMINISTIC', 'NOT_ACCEPTOR', 'NOT_ACCESSIBLE',
  'NOT_COACCESSIBLE', 'NOT_I_LABEL_SORTED', 'NOT_O_LABEL_SORTED',
  'NOT_STRING', 'NOT_TOP_SORTED', 'NO_EPSILONS', 'NO_I_EPSILONS',
  'NO_O_EPSILSONS', 'NULL_PROPERTIES', 'O_DETERMINISTIC', 'O_EPSILONS',
  'O_LABEL_INVARIANT_PROPERTIES', 'O_LABEL_SORTED',
  'POS_TRINARY_PROPERTIES', 'RM_SUPERFINAL_PROPERTIES',
  'SET_ARC_PROPERTIES', 'SET_FINAL_PROPERTIES', 'SET_START_PROPERTIES',
  'STATE_SORT_PROPERTIES', 'STRING', 'TOP_SORTED',
  'TRINARY_PROPERTIES', 'UNWEIGHTED', 'WEIGHTED',
  'WEIGHT_INVARIANT_PROPERTIES', 'Weight', '_Fst', '_MutableFst',
  '__builtins__', '__doc__', '__file__', '__name__', '__package__',
  '__pyx_capi__', '__test__', '_fst_error_fatal_old',
  '_get_compose_filter', '_get_queue_type', '_get_rand_arc_selection',
  '_get_replace_label_type', 'arcmap', 'compose', 'convert',
  'determinize', 'difference', 'disambiguate', 'epsnormalize',
  'equal', 'equivalent', 'intersect', 'isomorphic', 'prune', 'push', 'randequivalent', 'randgen', 'replace', 'reverse', 'rmepsilon',
  'shortestdistance', 'shortestpath', 'synchronize']
  </code></pre>