diff --git a/tablib/formats/_yaml.py b/tablib/formats/_yaml.py
index 0052b0f..f2359cf 100644
--- a/tablib/formats/_yaml.py
+++ b/tablib/formats/_yaml.py
@@ -13,16 +13,12 @@ except ImportError:
     else:
         import tablib.packages.yaml as yaml
 
-
 import tablib
 
-
-
 title = 'yaml'
 extensions = ('yaml', 'yml')
 
 
-
 def export_set(dataset):
     """Returns YAML representation of Dataset."""
 
@@ -52,6 +48,7 @@ def import_book(dbook, in_stream):
         data.dict = sheet['data']
         dbook.add_sheet(data)
 
+
 def detect(stream):
     """Returns True if given stream is valid YAML."""
     try:
diff --git a/tablib/packages/yaml3/composer.py b/tablib/packages/yaml3/composer.py
index 97c1306..572db8f 100644
--- a/tablib/packages/yaml3/composer.py
+++ b/tablib/packages/yaml3/composer.py
@@ -1,10 +1,8 @@
 __all__ = ['Composer', 'ComposerError']
 
 from .error import MarkedYAMLError
-from error import MarkedYAMLError
-from events import StreamEndEvent, StreamStartEvent, AliasEvent, SequenceEndEvent, SequenceStartEvent, MappingEndEvent,\
-    MappingStartEvent, ScalarEvent
-from nodes import MappingNode, ScalarNode, SequenceNode
+from .events import *
+from .nodes import *
 
 
 class ComposerError(MarkedYAMLError):
@@ -72,7 +70,8 @@ class Composer:
             return self.anchors[anchor]
         event = self.peek_event()
         anchor = event.anchor
-        if anchor is not None and anchor in self.anchors:
+        if anchor is not None:
+            if anchor in self.anchors:
                 raise ComposerError("found duplicate anchor %r; first occurence"
                                     % anchor, self.anchors[anchor].start_mark,
                                     "second occurence", event.start_mark)
diff --git a/tablib/packages/yaml3/constructor.py b/tablib/packages/yaml3/constructor.py
index 3fc9c7f..4468f54 100644
--- a/tablib/packages/yaml3/constructor.py
+++ b/tablib/packages/yaml3/constructor.py
@@ -5,13 +5,7 @@ __all__ = ['BaseConstructor', 'SafeConstructor', 'Constructor',
 from .error import *
 from .nodes import *
 
-import base64
-import binascii
-import collections
-import datetime
-import re
-import sys
-import types
+import collections, datetime, base64, binascii, re, sys, types
 
 class ConstructorError(MarkedYAMLError):
     pass
@@ -689,4 +683,3 @@ Constructor.add_multi_constructor(
 Constructor.add_multi_constructor(
     'tag:yaml.org,2002:python/object/new:',
     Constructor.construct_python_object_new)
-