Add set_shift to FlowMatchEulerDiscreteScheduler (#10269)

Author: hlky

src/diffusers/schedulers/scheduling_flow_match_euler_discrete.py

@@ -99,10 +99,19 @@ def __init__(
         self._step_index = None
         self._begin_index = None
 
+        self._shift = shift
+
         self.sigmas = sigmas.to("cpu")  # to avoid too much CPU/GPU communication
         self.sigma_min = self.sigmas[-1].item()
         self.sigma_max = self.sigmas[0].item()
 
+    @property
+    def shift(self):
+        """
+        The value used for shifting.
+        """
+        return self._shift
+
     @property
     def step_index(self):
         """
@@ -128,6 +137,9 @@ def set_begin_index(self, begin_index: int = 0):
         """
         self._begin_index = begin_index
 
+    def set_shift(self, shift: float):
+        self._shift = shift
+
     def scale_noise(
         self,
         sample: torch.FloatTensor,
@@ -236,7 +248,7 @@ def set_timesteps(
         if self.config.use_dynamic_shifting:
             sigmas = self.time_shift(mu, 1.0, sigmas)
         else:
-            sigmas = self.config.shift * sigmas / (1 + (self.config.shift - 1) * sigmas)
+            sigmas = self.shift * sigmas / (1 + (self.shift - 1) * sigmas)
 
         if self.config.shift_terminal:
             sigmas = self.stretch_shift_to_terminal(sigmas)