added logic to prevent seed_x and see_u from being specified at the s…

…ame time in __init__

src/UQpy/reliability/taylor_series/FORM.py

@@ -133,6 +133,8 @@ def __init__(
         self.x_record: list = []
         """Record of all iteration points in the parameter space **X**."""
 
+        if (seed_x is not None) and (seed_u is not None):
+            raise ValueError('UQpy: Only one input (seed_x or seed_u) may be provided')
         if self.seed_u is not None:
             self.run(seed_u=self.seed_u)
         elif self.seed_x is not None: