Issue #20326: Argument Clinic now uses a simple, unique signature to
annotate text signatures in docstrings, resulting in fewer false
positives.  "self" parameters are also explicitly marked, allowing
inspect.Signature() to authoritatively detect (and skip) said parameters.

Issue #20326: Argument Clinic now generates separate checksums for the
input and output sections of the block, allowing external tools to verify
that the input has not changed (and thus the output is not out-of-date).
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
index b78725e..80fa497 100644
--- a/Modules/_datetimemodule.c
+++ b/Modules/_datetimemodule.c
@@ -20,7 +20,7 @@
 module datetime
 class datetime.datetime "PyDateTime_DateTime *" "&PyDateTime_DateTimeType"
 [clinic start generated code]*/
-/*[clinic end generated code: checksum=da39a3ee5e6b4b0d3255bfef95601890afd80709]*/
+/*[clinic end generated code: output=da39a3ee5e6b4b0d input=78142cb64b9e98bc]*/
 
 /* We require that C int be at least 32 bits, and use int virtually
  * everywhere.  In just a few cases we use a temp long, where a Python
@@ -4159,7 +4159,7 @@
 [clinic start generated code]*/
 
 PyDoc_STRVAR(datetime_datetime_now__doc__,
-"now(type, tz=None)\n"
+"sig=($type, tz=None)\n"
 "Returns new datetime object representing current time local to tz.\n"
 "\n"
 "  tz\n"
@@ -4192,7 +4192,7 @@
 
 static PyObject *
 datetime_datetime_now_impl(PyTypeObject *type, PyObject *tz)
-/*[clinic end generated code: checksum=a6d3ad2c0ab6389075289af3467f7b8eb13f5f5c]*/
+/*[clinic end generated code: output=c8a47308483e579a input=80d09869c5267d00]*/
 {
     PyObject *self;