diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index dcb1561..30a97c0 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -29,8 +29,3 @@ repos:
   rev: 23.3.0
   hooks:
     - id: black
-
-- repo: https://github.com/PyCQA/flake8
-  rev: 4.0.1
-  hooks:
-    - id: flake8
diff --git a/sharrow/digital_encoding.py b/sharrow/digital_encoding.py
index 22a8b27..e260022 100644
--- a/sharrow/digital_encoding.py
+++ b/sharrow/digital_encoding.py
@@ -167,7 +167,7 @@ def digitize_by_dictionary(arr, bitwidth=8):
         bin_edges = (bins[1:] - bins[:-1]) / 2 + bins[:-1]
     except TypeError:
         # bins are not numeric
-        bin_map = {x: n for n, x in enumerate(bins)}
+        bin_map = {x:n for n,x in enumerate(bins)}
         u, inv = np.unique(arr.data, return_inverse=True)
         result.data = np.array([bin_map.get(x) for x in u])[inv].reshape(arr.shape)
         result.attrs["digital_encoding"] = {
diff --git a/sharrow/flows.py b/sharrow/flows.py
index 20636c1..e36e335 100644
--- a/sharrow/flows.py
+++ b/sharrow/flows.py
@@ -1741,6 +1741,9 @@ def __initialize_2(
                     if with_root_node_name is None:
                         with_root_node_name = self.tree.root_node_name
 
+                    if with_root_node_name is None:
+                        with_root_node_name = self.tree.root_node_name
+
                     root_dims = list(
                         presorted(
                             self.tree._graph.nodes[with_root_node_name]["dataset"].dims,
diff --git a/sharrow/relationships.py b/sharrow/relationships.py
index f3ffdc6..59ea78f 100644
--- a/sharrow/relationships.py
+++ b/sharrow/relationships.py
@@ -1037,7 +1037,7 @@ def drop_dims(self, dims, inplace=False, ignore_missing_dims=True):
         while boot_queue:
             b = boot_queue.pop()
             booted.add(b)
-            for up, dn, _n in obj._graph.edges.keys():
+            for (up, dn, _n) in obj._graph.edges.keys():
                 if up == b:
                     boot_queue.add(dn)
 
diff --git a/sharrow/selectors.py b/sharrow/selectors.py
index b057f89..927cfaa 100644
--- a/sharrow/selectors.py
+++ b/sharrow/selectors.py
@@ -134,6 +134,7 @@ def _filter(
             ds_ = ds
 
         if _names:
+
             result = (
                 getattr(ds_, _func)(**loaders)
                 .digital_encoding.strip(_names)