add reset and t0 method to the clock object

stimuli/time/_clock.py

@@ -58,6 +58,10 @@ def get_time(self) -> float:
         """
         return self.get_time_ns() / 1e9
 
+    @abstractmethod
+    def reset(self) -> None:
+        """Reset the clock to zero."""
+
 
 class Clock(BaseClock):
     """Clock which keeps track of time in nanoseconds.
@@ -77,8 +81,20 @@ def __init__(self) -> None:
             self._function = time.perf_counter_ns
         else:
             self._function = time.monotonic_ns
-        self._t0 = self._function()
+        self.reset()
 
     @copy_doc(BaseClock.get_time_ns)
     def get_time_ns(self) -> int:
         return self._function() - self._t0
+
+    def reset(self) -> None:
+        """Reset the clock to zero."""
+        self._t0 = self._function()
+
+    @property
+    def t0(self) -> int:
+        """The time of instantiation of the clock.
+
+        :type: :class:`int`
+        """
+        return self._t0

stimuli/time/tests/test_clock.py

@@ -20,3 +20,12 @@ def test_clock():
     t1 = clock.get_time_ns()
     t2 = clock.get_time_ns()
     assert t1 < t2
+
+
+def test_reset():
+    """Test the clock reset method."""
+    clock = Clock()
+    t0 = clock.t0
+    assert isinstance(t0, int)
+    clock.reset()
+    assert t0 < clock.t0