the bipartite graph constructor may fail when immutable=True

[dcoudert]

Steps To Reproduce

sage: B = BipartiteGraph(matrix([[1, 1], [1, 1]]), immutable=True)

Expected Behavior

build the bipartite graph

Actual Behavior

sage: B = BipartiteGraph(matrix([[1, 1], [1, 1]]), immutable=True)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Cell In[4], line 1
----> 1 B = BipartiteGraph(matrix([[Integer(1), Integer(1)], [Integer(1), Integer(1)]]), immutable=True)

File ~/sage/src/sage/graphs/bipartite_graph.py:478, in BipartiteGraph.__init__(self, data, partition, check, hash_labels, *args, **kwds)
    474 self.right = set(range(ncols, nrows + ncols))
    476 # ensure that the vertices exist even if there
    477 # are no associated edges (trac #10356)
--> 478 self.add_vertices(self.left)
    479 self.add_vertices(self.right)
    481 if kwds.get("multiedges", False):

File ~/sage/src/sage/graphs/generic_graph.py:11446, in GenericGraph.add_vertices(self, vertices)
  11411 def add_vertices(self, vertices):
  11412     """
  11413     Add vertices to the (di)graph from an iterable container of vertices.
  11414 
   (...)
  11444         [0, 6]
  11445     """
> 11446     return self._backend.add_vertices(vertices)

File ~/sage/src/sage/graphs/base/static_sparse_backend.pyx:603, in sage.graphs.base.static_sparse_backend.StaticSparseBackend.add_vertices()
    601         ValueError: graph is immutable; please change a copy instead (use function copy())
    602     """
--> 603     raise ValueError("graph is immutable; please change a copy instead (use function copy())")
    604 
    605 cpdef del_edge(self, object u, object v, object l, bint directed):

ValueError: graph is immutable; please change a copy instead (use function copy())

Additional Information

No response

Environment

• OS: all
• Sage Version: 10.6.beta3

Checklist

• I have searched the existing issues for a bug report that matches the one I want to file, without success.
• I have read the documentation and troubleshoot guide