Warn if model overwrites timeincrement

It seems to be a desired (and tested) feature to do so, but a typical user
will probably not want to do this. So, a warning makes sense.

src/oemof/solph/_models.py

@@ -160,7 +160,14 @@ def __init__(self, energysystem, discount_rate=None, **kwargs):
         self.name = kwargs.get("name", type(self).__name__)
 
         self.es = energysystem
-        self.timeincrement = kwargs.get("timeincrement", self.es.timeincrement)
+
+        if kwargs.get("timeincrement"):
+            msg = "Resetting timeincrement from EnergySystem in Model."
+            warnings.warn(msg, debugging.SuspiciousUsageWarning)
+
+            self.timeincrement = kwargs.get("timeincrement")
+        else:
+            self.timeincrement = self.es.timeincrement
 
         self.objective_weighting = kwargs.get(
             "objective_weighting", self.timeincrement
@@ -182,7 +189,7 @@ def __init__(self, energysystem, discount_rate=None, **kwargs):
         self.solver_results = None
         self.dual = None
         self.rc = None
-        
+
         if discount_rate is not None:
             self.discount_rate = discount_rate
         elif (
@@ -343,7 +350,6 @@ def _add_parent_block_variables(self):
                     for t in self.TIMESTEPS:
                         self.flow[o, i, t].setlb(0)
 
-
     def _add_child_blocks(self):
         """Method to add the defined child blocks for components that have
         been grouped in the defined constraint groups. This collects all the
@@ -453,4 +459,3 @@ def relax_problem(self):
         relaxer._apply_to(self)
 
         return self
-

tests/test_time_index.py

@@ -12,6 +12,7 @@
 import pytest
 
 from oemof import solph
+from oemof.tools import debugging
 
 
 def test_energysystem_with_datetimeindex_infer_last_interval():
@@ -151,7 +152,8 @@ def test_overwrite_timeincrement():
         infer_last_interval=True,
     )
     assert es.timeincrement[0] == 1
-    m = solph._models.Model(es, timeincrement=[3])
+    with pytest.warns(debugging.SuspiciousUsageWarning):
+        m = solph._models.Model(es, timeincrement=[3])
     assert m.timeincrement[0] == 3