Remove unused imports

Author: hugovk

examples/hello.py

@@ -1,6 +1,6 @@
 from datetime import datetime
 from flask import Flask, request, flash, url_for, redirect, \
-     render_template, abort
+     render_template
 from flask_sqlalchemy import SQLAlchemy
 
 

flask_sqlalchemy/__init__.py

@@ -29,7 +29,7 @@
 from sqlalchemy.orm.session import Session as SessionBase
 
 from flask_sqlalchemy.model import Model
-from ._compat import itervalues, string_types, to_str, xrange
+from ._compat import itervalues, string_types, xrange
 from .model import DefaultMeta
 
 __version__ = '2.3.2'