add remove utility function

theano/gof/tests/test_utils.py

 import theano
-from theano.gof.utils import give_variables_names, unique
+from theano.gof.utils import give_variables_names, unique, remove
 from theano.gof.python25 import all
 
 
@@ -34,3 +34,8 @@ def test_give_variables_names_small():
     give_variables_names(fgraph.variables)
     assert all(var.name for var in fgraph.variables)
     assert unique([var.name for var in fgraph.variables])
+
+def test_remove():
+    even = lambda x: x % 2 == 0
+    odd  = lambda x: x % 2 == 1
+    assert remove(even, range(5)) == filter(odd, range(5))

theano/gof/utils.py

@@ -410,3 +410,15 @@ def give_variables_names(variables):
                 "Maybe you've named some of the variables identically")
 
     return variables
+
+
+def remove(predicate, coll):
+    """ Return those items of collection for which predicate(item) is true.
+
+    >>> from itertoolz import remove
+    >>> def even(x):
+    ...     return x % 2 == 0
+    >>> remove(even, [1, 2, 3, 4])
+    [1, 3]
+    """
+    return filter(lambda x: not predicate(x), coll)