Improve doc strings

Objects/dictobject.c

@@ -3126,7 +3126,7 @@ _PyDict_MergeEx(PyObject *a, PyObject *b, int override)
 /*[clinic input]
 dict.copy
 
-D.copy() -> a shallow copy of D
+Returns a shallow copy of D.
 [clinic start generated code]*/
 
 static PyObject *
@@ -3508,7 +3508,7 @@ dict_setdefault_impl(PyDictObject *self, PyObject *key,
 /*[clinic input]
 dict.clear
 
-D.clear() -> None.  Remove all items from D.
+Removes all items.
 [clinic start generated code]*/
 
 static PyObject *
@@ -3706,7 +3706,7 @@ _PyDict_KeysSize(PyDictKeysObject *keys)
 /*[clinic input]
 dict.__sizeof__
 
-D.__sizeof__() -> size of D in memory, in bytes
+Returns size of D in memory, in bytes.
 [clinic start generated code]*/
 
 static PyObject *
@@ -5247,7 +5247,7 @@ PyTypeObject PyDictKeys_Type = {
 /*[clinic input]
 dict.keys
 
-D.keys() -> a set-like object providing a view on D's keys
+Returns a set-like object providing a view on D's keys.
 [clinic start generated code]*/
 
 static PyObject *
@@ -5359,7 +5359,7 @@ PyTypeObject PyDictItems_Type = {
 /*[clinic input]
 dict.items
 
-D.items() -> a set-like object providing a view on D's items
+Returns a set-like object providing a view on D's items.
 [clinic start generated code]*/
 
 static PyObject *
@@ -5449,7 +5449,7 @@ PyTypeObject PyDictValues_Type = {
 /*[clinic input]
 dict.values
 
-D.values() -> an object providing a view on D's values
+Returns an object providing a view on D's values.
 [clinic start generated code]*/
 
 static PyObject *