Pyomo.DoE: Add symbolic differentiation gradient calculation option as an alternative to finite different

pyomo/contrib/doe/__init__.py

@@ -8,8 +8,8 @@
 #  rights in this software.
 #  This software is distributed under the 3-clause BSD License.
 #  ___________________________________________________________________________
-from .doe import DesignOfExperiments, ObjectiveLib, FiniteDifferenceStep
-from .utils import rescale_FIM
+from .doe import DesignOfExperiments, ObjectiveLib, GradientMethod
+from .utils import rescale_FIM, ExperimentGradients
 
 # Deprecation errors for old Pyomo.DoE interface classes and structures
 from pyomo.common.deprecation import deprecated
@@ -45,3 +45,10 @@ def __init__(self, *args):
 class ModelOptionLib:
     def __init__(self, *args):
         raise RuntimeError(deprecation_message)
+
+@deprecated(
+    "Use of FiniteDifferenceStep in Pyomo.DoE is no longer supported. Use GradientMethod instead.", version='6.9.4'
+)
+class FiniteDifferenceStep:
+    def __init__(self, *args):
+        raise RuntimeError(deprecation_message)