chore: 添加虚拟环境到仓库

- 添加 backend_service/venv 虚拟环境
- 包含所有Python依赖包
- 注意：虚拟环境约393MB，包含12655个文件

backend_service/venv/lib/python3.13/site-packages/graphviz/graphs.py

@@ -0,0 +1,123 @@
+r"""Assemble DOT source code objects.
+
+Example:
+    >>> doctest_mark_exe()
+
+    >>> import graphviz
+    >>> dot = graphviz.Graph(comment='Mønti Pythøn ik den Hølie Grailen')
+
+    >>> dot.node('Møøse')
+    >>> dot.node('trained_by', 'trained by')
+    >>> dot.node('tutte', 'TUTTE HERMSGERVORDENBROTBORDA')
+
+    >>> dot.edge('Møøse', 'trained_by')
+    >>> dot.edge('trained_by', 'tutte')
+
+    >>> dot.node_attr['shape'] = 'rectangle'
+
+    >>> print(dot.source)  #doctest: +NORMALIZE_WHITESPACE
+    // Mønti Pythøn ik den Hølie Grailen
+    graph {
+        node [shape=rectangle]
+        "Møøse"
+        trained_by [label="trained by"]
+        tutte [label="TUTTE HERMSGERVORDENBROTBORDA"]
+        "Møøse" -- trained_by
+        trained_by -- tutte
+    }
+
+    >>> dot.render('doctest-output/m00se.gv').replace('\\', '/')
+    'doctest-output/m00se.gv.pdf'
+"""
+
+import typing
+
+from .encoding import DEFAULT_ENCODING
+from . import _tools
+from . import dot
+from . import jupyter_integration
+from . import piping
+from . import rendering
+from . import unflattening
+
+__all__ = ['Graph', 'Digraph']
+
+
+class BaseGraph(dot.Dot,
+                rendering.Render,
+                jupyter_integration.JupyterIntegration, piping.Pipe,
+                unflattening.Unflatten):
+    """Dot language creation and source code rendering."""
+
+    @_tools.deprecate_positional_args(supported_number=1, ignore_arg='self')
+    def __init__(self, name: typing.Optional[str] = None,
+                 comment: typing.Optional[str] = None,
+                 filename=None, directory=None,
+                 format: typing.Optional[str] = None,
+                 engine: typing.Optional[str] = None,
+                 encoding: typing.Optional[str] = DEFAULT_ENCODING,
+                 graph_attr=None, node_attr=None, edge_attr=None,
+                 body=None,
+                 strict: bool = False, *,
+                 renderer: typing.Optional[str] = None,
+                 formatter: typing.Optional[str] = None) -> None:
+        if filename is None and name is not None:
+            filename = f'{name}.{self._default_extension}'
+
+        super().__init__(name=name, comment=comment,
+                         graph_attr=graph_attr,
+                         node_attr=node_attr, edge_attr=edge_attr,
+                         body=body, strict=strict,
+                         filename=filename, directory=directory,
+                         encoding=encoding,
+                         format=format, engine=engine,
+                         renderer=renderer, formatter=formatter)
+
+    @property
+    def source(self) -> str:
+        """The generated DOT source code as string."""
+        return ''.join(self)
+
+
+class Graph(dot.GraphSyntax, BaseGraph):
+    """Graph source code in the DOT language.
+
+    Args:
+        name: Graph name used in the source code.
+        comment: Comment added to the first line of the source.
+        filename: Filename for saving the source
+            (defaults to ``name`` + ``'.gv'``).
+        directory: (Sub)directory for source saving and rendering.
+        format: Rendering output format (``'pdf'``, ``'png'``, ...).
+        engine: Layout command used (``'dot'``, ``'neato'``, ...).
+        renderer: Output renderer used (``'cairo'``, ``'gd'``, ...).
+        formatter: Output formatter used (``'cairo'``, ``'gd'``, ...).
+        encoding: Encoding for saving the source.
+        graph_attr: Mapping of ``(attribute, value)`` pairs for the graph.
+        node_attr: Mapping of ``(attribute, value)`` pairs set for all nodes.
+        edge_attr: Mapping of ``(attribute, value)`` pairs set for all edges.
+        body: Iterable of verbatim lines (including their final newline)
+            to add to the graph ``body``.
+        strict (bool): Rendering should merge multi-edges.
+
+    Note:
+        All parameters are `optional` and can be changed under their
+        corresponding attribute name after instance creation.
+    """
+
+    @property
+    def directed(self) -> bool:
+        """``False``"""
+        return False
+
+
+class Digraph(dot.DigraphSyntax, BaseGraph):
+    """Directed graph source code in the DOT language."""
+
+    if Graph.__doc__ is not None:
+        __doc__ += Graph.__doc__.partition('.')[2]
+
+    @property
+    def directed(self) -> bool:
+        """``True``"""
+        return True