Three lint errors remain.

app/specs/container.py

@@ -23,8 +23,7 @@ class ContainerSpec(Spec):
         mountpoint: str,
         notify=None,
     ):
-        """
-        Create a new ContainerSpec object.
+        """Create a new ContainerSpec object.
 
         Args:
             name: name of the spec (used as an identifier)
@@ -36,7 +35,7 @@ class ContainerSpec(Spec):
                 perform a specified backup and output this data to stdout. This
                 output then gets piped to a backup file.
             extension: the extension of the backup files.
-            mountpoint:
+            mountpoint: I don't actually know, this never gets used
             notify: notifier object (may be None)
         """
         super().__init__(name, destination, limit, extension, notify)

app/specs/directory.py

@@ -26,8 +26,7 @@ class DirectorySpec(Spec):
         extension: str,
         notify=None,
     ):
-        """
-        Initialize a new DirectorySpec object.
+        """Initialize a new DirectorySpec object.
 
         Args:
             name: name of the spec

app/specs/spec.py

@@ -41,7 +41,8 @@ class Spec:
             name: name of the spec
             destination: directory where the backups shall reside
             limit: max amount of backups
-            notifier: notifier object
+            extension: file extension of the backup files
+            notify: notifier object to send IFTT notifications
         """
         self.name = name
         self.destination = Path(destination)
@@ -119,5 +120,6 @@ class Spec:
     def to_dict(self):
         """Export the class as a dictionary.
 
-        This function should be imnplemented by the subclasses."""
+        This function should be imnplemented by the subclasses.
+        """
         raise NotImplementedError()

app/specs/volume.py

@@ -1,3 +1,6 @@
+"""Module defining a Docker volume-based spec."""
+
+
 from .spec import Spec
 from typing import Union
 from pathlib import Path
@@ -25,6 +28,18 @@ class VolumeSpec(Spec):
         extension: str,
         notify=None,
     ):
+        """Initialize a new VolumeSpec object.
+
+        Args:
+            name: name of the spec
+            volume: Docker volume to back up
+            image: base image to use to run backup command
+            destination: where to store the backup files
+            limit: max backup files to keep
+            command: backup command to run within the base image
+            extension: file extension of the backup files
+            notify: Notifier object
+        """
         super().__init__(name, destination, limit, extension, notify)
 
         self.volume = volume
@@ -32,6 +47,7 @@ class VolumeSpec(Spec):
         self.command = command
 
     def backup(self):
+        """Create a new backup."""
         # Remove excess backups
         self.remove_backups()
 
@@ -40,8 +56,10 @@ class VolumeSpec(Spec):
             datetime.now().strftime("%Y-%m-%d_%H-%M-%S"), self.extension
         )
 
+        base_cmd = "docker run --rm -v '{}:/from' -v '{}:/to' -w /from '{}' {}"
+
         process = subprocess.run(
-            "docker run --rm -v '{}:/from' -v '{}:/to' -w /from '{}' {}".format(
+            base_cmd.format(
                 self.volume,
                 self.destination,
                 self.image,