Clean up lint errors

src/pip/_internal/models/format_control.py

@@ -2,8 +2,8 @@ import operator
 from pip._vendor.packaging.utils import canonicalize_name
 
 from pip._internal.exceptions import CommandError
-from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 from pip._internal.utils.models import Base
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
 if MYPY_CHECK_RUNNING:
     from typing import Optional, Set, FrozenSet
@@ -29,8 +29,10 @@ class FormatControl(Base):
         # type: (object) -> bool
         if isinstance(other, self.__class__):
             if self.__slots__ == other.__slots__:
-                 attr_getters = [operator.attrgetter(attr) for attr in self.__slots__]
-                 return all(getter(self) == getter(other) for getter in attr_getters)
+                attr_getters = [operator.attrgetter(attr)
+                                for attr in self.__slots__]
+                return all(getter(self) == getter(other)
+                           for getter in attr_getters)
 
         return False
 

src/pip/_internal/models/index.py

@@ -1,4 +1,5 @@
 from pip._vendor.six.moves.urllib import parse as urllib_parse
+
 from pip._internal.utils.models import Base
 
 
@@ -6,7 +7,8 @@ class PackageIndex(Base):
     """Represents a Package Index and provides easier access to endpoints
     """
 
-    __slots__ = ["url", "netloc", "simple_url", "pypi_url", "file_storage_domain"]
+    __slots__ = ['url', 'netloc', 'simple_url', 'pypi_url',
+                 'file_storage_domain']
 
     def __init__(self, url, file_storage_domain):
         # type: (str, str) -> None

src/pip/_internal/models/scheme.py

@@ -7,6 +7,7 @@ https://docs.python.org/3/install/index.html#alternate-installation.
 
 from pip._internal.utils.models import Base
 
+
 class Scheme(Base):
     """A Scheme holds paths which are used as the base directories for
     artifacts associated with a Python package.

src/pip/_internal/models/selection_prefs.py

@@ -12,7 +12,8 @@ class SelectionPreferences(Base):
     and installing files.
     """
 
-    __slots__ = ['allow_yanked', 'allow_all_prereleases', 'format_control', 'prefer_binary', 'ignore_requires_python']
+    __slots__ = ['allow_yanked', 'allow_all_prereleases', 'format_control',
+                 'prefer_binary', 'ignore_requires_python']
 
     # Don't include an allow_yanked default value to make sure each call
     # site considers whether yanked releases are allowed. This also causes

src/pip/_internal/utils/models.py

@@ -4,10 +4,12 @@
 # mypy: disallow-untyped-defs=False
 
 import operator
+from typing import List
 
 
 class Base(object):
-    __slots__ = []
+    __slots__ = []  # type: List[str]
+
 
 class KeyBasedCompareMixin(Base):
     """Provides comparison capabilities that is based on a key