fix(hansbug): try simplify the saving of the images

test/entry/cli/test_graph.py

@@ -7,7 +7,7 @@ import zlib
 
 import pytest
 from click.testing import CliRunner
-from hbutils.testing import cmdv
+from hbutils.testing import cmdv, OS
 
 from treevalue import FastTreeValue, dump, graphics
 from treevalue.entry.cli import treevalue_cli
@@ -244,4 +244,7 @@ class TestEntryCliGraph:
                 assert result.exit_code == 0, f'Runtime Error (exitcode {result.exit_code}), ' \
                                               f'The output is:\n{result.output}'
                 assert os.path.exists('test_graph.svg')
-                assert os.path.getsize('test_graph.svg') <= 1000
+                if OS.windows:
+                    assert os.path.getsize('test_graph.svg') <= 2000
+                else:
+                    assert os.path.getsize('test_graph.svg') <= 1000

treevalue/entry/cli/graph.py

 import codecs
 import os
-import shutil
-import tempfile
 import warnings
 from collections import OrderedDict
 from functools import partial
@@ -61,10 +59,7 @@ def _save_source_code(g: Digraph, path: str):
 
 
 def _save_image(g: Digraph, path: str, fmt: str):
-    with tempfile.TemporaryDirectory() as tmpdir:
-        with tempfile.NamedTemporaryFile(dir=tmpdir) as tmpfile:
-            svg_file = g.render(tmpfile.name, format=fmt)
-            shutil.copy(svg_file, path)
+    g.render(path, format=fmt)
 
 
 _IMAGE_FMTS = {'svg', 'png'}