gh-40779: removing some unused imports in pyx files
    
found using
`
cython-lint src/sage/ | grep imported
`
### 📝 Checklist

- [x] The title is concise and informative.
- [x] The description explains in detail what this PR is about.
    
URL: #40779
Reported by: Frédéric Chapoton
Reviewer(s): David Coudert, Vincent Macri

Author: Release Manager

src/sage/graphs/path_enumeration.pyx

@@ -41,8 +41,6 @@ from libcpp.vector cimport vector
 from sage.data_structures.pairing_heap cimport PairingHeap
 from sage.rings.integer_ring import ZZ
 
-import copy
-
 
 def all_paths(G, start, end, use_multiedges=False, report_edges=False, labels=False):
     """

src/sage/libs/gap/element.pyx

@@ -28,7 +28,6 @@ from sage.rings.integer_ring import ZZ
 from sage.rings.rational_field import QQ
 from sage.rings.real_double import RDF
 
-from sage.groups.perm_gps.permgroup_element cimport PermutationGroupElement
 from sage.combinat.permutation import Permutation
 from sage.structure.coerce cimport coercion_model as cm
 
@@ -1473,7 +1472,6 @@ cdef class GapElement(RingElement):
             return FreeGroup_class(names, gap_group=self)
 
         elif self.IsFpGroup():
-            from sage.groups.free_group import FreeGroup
             from sage.groups.finitely_presented import FinitelyPresentedGroup
             # names = tuple(str(g).replace(".", "_") for g in self.FreeGroupOfFpGroup().GeneratorsOfGroup())
             F = self.FreeGroupOfFpGroup().sage()

src/sage/matrix/matrix_modn_sparse.pyx

@@ -90,32 +90,21 @@ cimport sage.libs.linbox.linbox as linbox
 
 from sage.arith.misc import is_prime
 from sage.data_structures.binary_search cimport *
-from sage.ext.stdsage cimport PY_NEW
-from sage.libs.flint.fmpz cimport fmpz_get_mpz, fmpz_set_mpz
-from sage.libs.flint.fmpz_mat cimport fmpz_mat_entry
-from sage.libs.gmp.mpz cimport mpz_set
-from sage.libs.linbox.conversion cimport (get_method,
-                                          METHOD_DEFAULT,
+from sage.libs.linbox.conversion cimport (METHOD_DEFAULT,
                                           METHOD_DENSE_ELIMINATION,
                                           METHOD_SPARSE_ELIMINATION,
                                           METHOD_BLACKBOX,
                                           METHOD_WIEDEMANN,
-                                          new_linbox_matrix_modn_sparse,
-                                          new_linbox_matrix_integer_sparse,
-                                          new_linbox_vector_integer_dense,
-                                          new_sage_vector_integer_dense)
+                                          new_linbox_matrix_modn_sparse)
 from sage.matrix.args cimport SparseEntry, MatrixArgs_init
 from sage.matrix.matrix2 import Matrix as Matrix2
 from sage.matrix.matrix_dense cimport Matrix_dense
-from sage.matrix.matrix_integer_dense cimport Matrix_integer_dense
 from sage.matrix.matrix_sparse cimport Matrix_sparse
 from sage.misc.verbose import verbose, get_verbose
-from sage.modules.vector_integer_dense cimport Vector_integer_dense
 from sage.modules.vector_integer_sparse cimport *
 from sage.modules.vector_modn_sparse cimport *
 from sage.rings.fast_arith cimport arith_int
 from sage.rings.finite_rings.integer_mod cimport IntegerMod_int, IntegerMod_abstract
-from sage.rings.integer cimport Integer
 from sage.rings.integer_ring import ZZ
 from sage.structure.element cimport Matrix
 
@@ -130,6 +119,7 @@ ai = arith_int()
 # Github Issue #12679.
 MAX_MODULUS = 46341
 
+
 cdef class Matrix_modn_sparse(Matrix_sparse):
     def __cinit__(self):
         nr = self._nrows

src/sage/modules/free_module_element.pyx

@@ -117,7 +117,7 @@ from cpython.slice cimport PySlice_GetIndicesEx
 
 from sage.categories.rings import Rings
 from sage.structure.sequence import Sequence
-from sage.structure.element cimport Element, RingElement, Vector
+from sage.structure.element cimport Element, Vector
 from sage.structure.element import canonical_coercion
 from sage.structure.richcmp cimport richcmp_not_equal, richcmp, rich_to_bool
 

src/sage/rings/ring.pyx

@@ -108,10 +108,8 @@ This is to test a deprecation::
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
 
-from sage.misc.cachefunc import cached_method
 from sage.misc.superseded import deprecation
 
-from sage.structure.coerce cimport coercion_model
 from sage.structure.parent cimport Parent
 from sage.structure.category_object cimport check_default_category
 from sage.categories.rings import Rings