gh-35553: cython-lint cleaning in combinat/
    
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### 📚 Description

Some fixes about unused imports and variables in pyx files inside
`combinat`

found using
```
cython-lint --ignore=E,W src/sage/combinat/
```

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- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation accordingly.

### ⌛ Dependencies

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URL: #35553
Reported by: Frédéric Chapoton
Reviewer(s): Matthias Köppe

Author: Release Manager

src/sage/combinat/crystals/pbw_datum.pyx

@@ -25,7 +25,6 @@ AUTHORS:
 #from sage.misc.lazy_attribute import lazy_attribute
 from sage.misc.cachefunc import cached_method
 from sage.combinat.root_system.cartan_type import CartanType
-from sage.combinat.root_system.coxeter_group import CoxeterGroup
 from sage.combinat.root_system.root_system import RootSystem
 from sage.combinat.root_system.braid_move_calculator import BraidMoveCalculator
 
@@ -450,7 +449,7 @@ cpdef list enhance_braid_move_chain(braid_move_chain, cartan_type):
     """
     cdef int i, j
     cdef int k, pos, first, last
-    cdef tuple interval_of_change, cartan_sub_matrix
+    cdef tuple cartan_sub_matrix
     cdef list output_list = []
     output_list.append( (None, None) )
     cdef tuple previous_word = <tuple> (braid_move_chain[0])

src/sage/combinat/crystals/spins.pyx

@@ -44,7 +44,6 @@ representing the elements of the spin crystal by sequences of signs
 
 from cpython.object cimport Py_EQ, Py_NE, Py_LE, Py_GE, Py_LT, Py_GT
 from cysignals.memory cimport sig_malloc, sig_free
-from sage.misc.cachefunc import cached_method
 from sage.misc.lazy_attribute import lazy_attribute
 from sage.structure.unique_representation import UniqueRepresentation
 from sage.structure.parent cimport Parent

src/sage/combinat/crystals/tensor_product_element.pyx

@@ -30,7 +30,6 @@ AUTHORS:
 #                  https://www.gnu.org/licenses/
 #****************************************************************************
 
-from cpython.object cimport Py_LT, Py_LE, Py_EQ, Py_NE, Py_GT, Py_GE
 from sage.structure.parent cimport Parent
 
 from sage.misc.cachefunc import cached_method, cached_in_parent_method
@@ -1642,7 +1641,7 @@ cdef class TensorProductOfQueerSuperCrystalsElement(TensorProductOfRegularCrysta
 
 
 cdef class InfinityQueerCrystalOfTableauxElement(TensorProductOfQueerSuperCrystalsElement):
-    def __init__(self, parent, list, row_lengths=[]):
+    def __init__(self, parent, list, row_lengths=None):
         """
         Initialize ``self``.
 
@@ -1654,6 +1653,8 @@ cdef class InfinityQueerCrystalOfTableauxElement(TensorProductOfQueerSuperCrysta
             [[4, 4, 4, 4, 2, 1], [3, 3, 3], [2, 2], [1]]
             sage: TestSuite(t).run()
         """
+        if row_lengths is None:
+            row_lengths = []
         if not row_lengths and list and not isinstance(list[0], parent.letters.element_class):
             ret = []
             L = parent.letters

src/sage/combinat/degree_sequences.pyx

@@ -264,23 +264,19 @@ Checking the consistency of enumeration and test::
     than a couple of minutes.
 """
 
-#*****************************************************************************
+# ****************************************************************************
 #       Copyright (C) 2011 Nathann Cohen <[email protected]>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation, either version 2 of the License, or
 # (at your option) any later version.
-#                  http://www.gnu.org/licenses/
-#*****************************************************************************
+#                  https://www.gnu.org/licenses/
+# ****************************************************************************
 
-
-from libc.string cimport memset
 from cysignals.memory cimport check_calloc, sig_free
 from cysignals.signals cimport sig_on, sig_off
 
-from sage.rings.integer cimport Integer
-
 
 cdef unsigned char * seq
 cdef list sequences

src/sage/combinat/designs/designs_pyx.pyx

@@ -224,7 +224,7 @@ def is_group_divisible_design(groups,blocks,v,G=None,K=None,lambd=1,verbose=Fals
         (True, [[0], [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12]])
     """
     cdef int n = v
-    cdef int i,ii,j,jj,s,isok
+    cdef int i,ii,j,jj,s
     cdef int l = lambd
     cdef bint guess_groups = groups is None
 

src/sage/combinat/designs/evenly_distributed_sets.pyx

@@ -23,7 +23,7 @@ from libc.string cimport memset, memcpy
 
 from cysignals.memory cimport check_malloc, check_calloc, sig_free
 
-from sage.rings.integer cimport Integer,smallInteger
+from sage.rings.integer cimport smallInteger
 
 cdef class EvenlyDistributedSetsBacktracker:
     r"""
@@ -212,7 +212,7 @@ cdef class EvenlyDistributedSetsBacktracker:
         self.up_to_isom = bool(up_to_isomorphism)
         self.count      = 0
 
-        cdef unsigned int i,j,ell
+        cdef unsigned int i,j
 
         if not K.is_field():
             raise ValueError("{} is not a field".format(K))

src/sage/combinat/designs/gen_quadrangles_with_spread.pyx

@@ -286,7 +286,6 @@ def generalised_quadrangle_hermitian_with_ovoid(const int q):
     from sage.arith.misc import is_prime_power
 
     GU = libgap.GU(4, q)
-    H = libgap.InvariantSesquilinearForm(GU)["matrix"]
     Fq = libgap.GF(q * q)
     zero = libgap.Zero(Fq)
     one = libgap.One(Fq)
@@ -310,14 +309,13 @@ def generalised_quadrangle_hermitian_with_ovoid(const int q):
     lines = [list(map(lambda x: int(x - 1), b)) for b in lines]  # convert to int
     # lines defines the GQ H(3, q^2)
 
-
     # to find an ovoid, we embed H(3,q^2) in H(4,q^2)
     # the embedding is (a,b,c,d) -> (a,b,0,c,d)
     # then we find a point in the latter and not in the former
     # this point will be collinear (in H(3,q^2)) to all points in an ovoid
     if q % 2 == 1:
-        (p, k) = is_prime_power(q, get_data=True)
-        a = (p-1) // 2
+        p, _ = is_prime_power(q, get_data=True)
+        a = (p - 1) // 2
         aGap = zero
         for i in range(a):
             aGap += one

src/sage/combinat/designs/orthogonal_arrays_find_recursive.pyx

@@ -47,7 +47,7 @@ Functions
 
 from sage.misc.cachefunc import cached_function
 from .orthogonal_arrays import orthogonal_array
-from sage.rings.integer cimport Integer, smallInteger
+from sage.rings.integer cimport smallInteger
 from sage.arith.misc import prime_powers
 
 @cached_function

src/sage/combinat/designs/subhypergraph_search.pyx

@@ -119,7 +119,7 @@ Methods
 
 from libc.stdlib cimport qsort
 from libc.stdint cimport uint64_t
-from cysignals.memory cimport sig_malloc, sig_calloc, sig_realloc, sig_free
+from cysignals.memory cimport sig_malloc, sig_calloc, sig_free
 
 ctypedef struct hypergraph:
     int n
@@ -490,7 +490,6 @@ cdef class SubHypergraphSearch:
         cdef hypergraph h1 = self.h1
         cdef hypergraph h2 = self.h2
         cdef hypergraph tmp1 = self.tmp1
-        cdef hypergraph tmp2 = self.tmp2
         cdef int * step = self.step
 
         if h1.n<h2.n or h1.m<h2.m:

src/sage/combinat/enumeration_mod_permgroup.pyx

@@ -274,7 +274,6 @@ cpdef set orbit(list sgs, ClonableIntArray v):
     cdef set to_analyse, new_to_analyse
     cdef ClonableIntArray list_test, child
     cdef PermutationGroupElement x
-    cdef list out
     l = len(v)
     to_analyse = set([v])
     for i in range(l-1):