NameError in twtl.py

[dishakamale]

When I run twtl.py on branch feature/port_antlr4, I get the following error:

Traceback (most recent call last):
  File "examples_tcs.py", line 137, in <module>
    case1_synthesis(phi, '../data/ts_synthesis.yaml')
  File "examples_tcs.py", line 43, in case1_synthesis
    _, dfa_0, dfa_inf, bdd = twtl.translate(formula, kind='both', norm=True)
  File "/home/disha/Lehigh/twtl_antlr4/twtl/twtl/twtl.py", line 259, in translate
    ast = TWTLAbstractSyntaxTreeExtractor().visit(t)
NameError: global name 't' is not defined