sagemathgh-38790: avoid some type comparisons in combinat
    
just a few minor changes, about using `isinstance` when possible

### 📝 Checklist

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.
    
URL: sagemath#38790
Reported by: Frédéric Chapoton
Reviewer(s): Travis Scrimshaw

Author: Release Manager

src/sage/combinat/cluster_algebra_quiver/quiver.py

@@ -232,7 +232,8 @@ def __init__(self, data, frozen=None, user_labels=None):
                                    values))
 
         # constructs a quiver from a mutation type
-        if type( data ) in [QuiverMutationType_Irreducible,QuiverMutationType_Reducible]:
+        if isinstance(data, (QuiverMutationType_Irreducible,
+                             QuiverMutationType_Reducible)):
             if frozen is not None:
                 print('The input specifies a mutation type, so the'
                       ' additional parameter frozen is ignored.'
@@ -1950,10 +1951,15 @@ def is_mutation_finite( self, nr_of_checks=None, return_path=False ):
             path = None
         elif not return_path and self._mutation_type == 'undetermined infinite mutation type':
             is_finite = False
-        elif type( self._mutation_type ) in [QuiverMutationType_Irreducible, QuiverMutationType_Reducible] and self._mutation_type.is_mutation_finite():
+        elif (isinstance(self._mutation_type, (QuiverMutationType_Irreducible,
+                                               QuiverMutationType_Reducible))
+              and self._mutation_type.is_mutation_finite()):
             is_finite = True
             path = None
-        elif not return_path and type( self._mutation_type ) in [QuiverMutationType_Irreducible, QuiverMutationType_Reducible] and not self._mutation_type.is_mutation_finite():
+        elif (not return_path and isinstance(self._mutation_type,
+                                             (QuiverMutationType_Irreducible,
+                                              QuiverMutationType_Reducible))
+              and not self._mutation_type.is_mutation_finite()):
             is_finite = False
         else:
             # turning dg_component into a canonical form

src/sage/combinat/cluster_algebra_quiver/quiver_mutation_type.py

@@ -67,7 +67,9 @@ def __call__(self, *args):
             _mutation_type_error(data)
 
         # check for reducible types
-        if all(type(data_component) in [list, tuple, QuiverMutationType_Irreducible] for data_component in data):
+        if all(isinstance(data_component, (list, tuple,
+                                           QuiverMutationType_Irreducible))
+               for data_component in data):
             if len(data) == 1:
                 return QuiverMutationType(data[0])
             else:

src/sage/combinat/core.py

@@ -102,7 +102,7 @@ def __init__(self, parent, core):
             raise ValueError("%s is not a %s-core" % (part, k))
         CombinatorialElement.__init__(self, parent, core)
 
-    def __eq__(self, other):
+    def __eq__(self, other) -> bool:
         """
         Test for equality.
 
@@ -123,7 +123,7 @@ def __eq__(self, other):
                     self.parent().k == other.parent().k)
         return False
 
-    def __ne__(self, other):
+    def __ne__(self, other) -> bool:
         """
         Test for un-equality.
 
@@ -169,7 +169,7 @@ def __hash__(self):
             self._hash = hash(tuple(self._list)) + hash(self.parent().k)
         return self._hash
 
-    def _latex_(self):
+    def _latex_(self) -> str:
         r"""
         Output the LaTeX representation of this core as a partition.
 
@@ -449,7 +449,7 @@ def weak_le(self, other):
             ...
             ValueError: the two cores do not have the same k
         """
-        if type(self) is type(other):
+        if isinstance(other, Core):
             if self.k() != other.k():
                 raise ValueError("the two cores do not have the same k")
         else:
@@ -504,14 +504,14 @@ def strong_le(self, other):
             ...
             ValueError: the two cores do not have the same k
         """
-        if type(self) is type(other):
+        if isinstance(other, Core):
             if self.k() != other.k():
                 raise ValueError("the two cores do not have the same k")
         else:
             other = Core(other, self.k())
         return other.contains(self)
 
-    def contains(self, other):
+    def contains(self, other) -> bool:
         r"""
         Check whether ``self`` contains ``other``.
 

src/sage/combinat/root_system/integrable_representations.py

@@ -1046,7 +1046,7 @@ def modular_characteristic(self, mu=None):
             sage: [V.modular_characteristic(x) for x in V.dominant_maximal_weights()]
             [11/56, -1/280, 111/280]
         """
-        if type(mu) is tuple:
+        if isinstance(mu, tuple):
             n = mu
         else:
             n = self.from_weight(mu)

src/sage/combinat/shard_order.py

@@ -127,7 +127,7 @@ def __le__(self, other):
             sage: e1 <= e0
             False
         """
-        if type(self) is not type(other) or len(self) != len(other):
+        if not isinstance(other, ShardPosetElement) or len(self) != len(other):
             raise TypeError("these are not comparable")
         if self.runs == other.runs:
             return True