diff --git a/lark/lark.py b/lark/lark.py
index 6b065f8..d270456 100644
--- a/lark/lark.py
+++ b/lark/lark.py
@@ -112,9 +112,6 @@ class Lark:
             self.source = grammar.name
         except AttributeError:
             self.source = '<string>'
-            cache_file = "larkcache_%s" % str(hash(grammar)%(2**32))
-        else:
-            cache_file = "larkcache_%s" % os.path.basename(self.source)
 
         # Drain file-like objects to get their contents
         try:
diff --git a/lark/load_grammar.py b/lark/load_grammar.py
index 2f48cb1..76c9b10 100644
--- a/lark/load_grammar.py
+++ b/lark/load_grammar.py
@@ -528,7 +528,7 @@ def import_grammar(grammar_path, base_paths=[]):
 def import_from_grammar_into_namespace(grammar, namespace, aliases):
     imported_terms = dict(grammar.term_defs)
     imported_rules = {n:(n,t,o) for n,t,o in grammar.rule_defs}
-    
+
     term_defs = []
     rule_defs = []
 
diff --git a/lark/parse_tree_builder.py b/lark/parse_tree_builder.py
index a6e28e5..d53b75d 100644
--- a/lark/parse_tree_builder.py
+++ b/lark/parse_tree_builder.py
@@ -1,7 +1,5 @@
 from .exceptions import GrammarError
-from .utils import suppress
 from .lexer import Token
-from .grammar import Rule
 from .tree import Tree
 from .visitors import InlineTransformer # XXX Deprecated
 
diff --git a/lark/parsers/resolve_ambig.py b/lark/parsers/resolve_ambig.py
index 2470eb9..da81594 100644
--- a/lark/parsers/resolve_ambig.py
+++ b/lark/parsers/resolve_ambig.py
@@ -36,7 +36,7 @@ def _compare_drv(tree1, tree2):
     except AttributeError:
         rule2 = None
 
-    if None == rule1 == rule2:
+    if rule1 is None and rule2 is None:
         return compare(tree1, tree2)
     elif rule1 is None:
         return -1
diff --git a/lark/reconstruct.py b/lark/reconstruct.py
index a21f155..1c769e8 100644
--- a/lark/reconstruct.py
+++ b/lark/reconstruct.py
@@ -100,10 +100,8 @@ class Reconstructor:
         for origin, rule_aliases in aliases.items():
             for alias in rule_aliases:
                 yield Rule(origin, [Terminal(alias)], MakeMatchTree(origin.name, [NonTerminal(alias)]))
-            
-            yield Rule(origin, [Terminal(origin.name)], MakeMatchTree(origin.name, [origin]))
-        
 
+            yield Rule(origin, [Terminal(origin.name)], MakeMatchTree(origin.name, [origin]))
 
     def _match(self, term, token):
         if isinstance(token, Tree):
@@ -127,4 +125,3 @@ class Reconstructor:
 
     def reconstruct(self, tree):
         return ''.join(self._reconstruct(tree))
-
diff --git a/lark/tools/standalone.py b/lark/tools/standalone.py
index 1f664b6..89ca4e0 100644
--- a/lark/tools/standalone.py
+++ b/lark/tools/standalone.py
@@ -45,9 +45,7 @@ from collections import defaultdict
 
 import lark
 from lark import Lark
-from lark.parsers.lalr_analysis import Shift, Reduce
-
-from ..grammar import Rule
+from lark.parsers.lalr_analysis import Reduce
 
 _dir = path.dirname(__file__)
 _larkdir = path.join(_dir, path.pardir)