Importer can't import block after block_renaming

[Gashmen]

Hello @mozman.

I encountered a peculiarity when Importing a block after renaming in library_doc.
So I have dxf_file_lib like a lib, with all blocks. And when I want to import block that I need importer won't add in doc.blocks.

Previous, I changed names in dxf_file_lib with using function doc.blocks.rename_block(old_name,new_name).
I changed all names that started with U, and create some structures in block like: if block has inserts, that need to rename it.
And example I has blocks like : 'Main_name', 'Main_name_U45', 'Main_name_U587', 'Main_name_U587_U659' and ...

On JPG N1 I want to show all names of block_layout.

After I used code:
doc = ezdxf.readfile(dxf_file_lib)
doc_new_file = ezdxf.new(dxfversion='AC1024')
importer = Importer(doc, doc_new_file)
list_with_block_names = [block.dxf.name for block in doc.blocks if '*' not in block.dxf.name]
for i in list_with_block_names:
importer.import_block(i)
importer.finalize()

And then:

I was checked the dxf_file_lib in Notepad and I saw, that they have names U22 and U22 is AcDbBlockReference or Insert

What I need to do for fix it? Easy way is to change it with open dxf like txt file and search U_blocks, but mb you have a solution.
Thank you!

[mozman]

[Gashmen]

Thank you! It's very sad :(