Removed COMMA token from explicit lexing script (was elready in operator list).

src/parser.py

@@ -436,7 +436,6 @@ class Parser(BisonParser):
     [a-zA-Z]  { returntoken(IDENTIFIER); }
     "("       { returntoken(LPAREN); }
     ")"       { returntoken(RPAREN); }
-    ","       { returntoken(COMMA); }
     """ + operators + r"""
     "raise"   { returntoken(RAISE); }
     "graph"   { returntoken(GRAPH); }