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/sympy/utilities/source.py

@@ -0,0 +1,40 @@
+"""
+This module adds several functions for interactive source code inspection.
+"""
+
+
+def get_class(lookup_view):
+    """
+    Convert a string version of a class name to the object.
+
+    For example, get_class('sympy.core.Basic') will return
+    class Basic located in module sympy.core
+    """
+    if isinstance(lookup_view, str):
+        mod_name, func_name = get_mod_func(lookup_view)
+        if func_name != '':
+            lookup_view = getattr(
+                __import__(mod_name, {}, {}, ['*']), func_name)
+            if not callable(lookup_view):
+                raise AttributeError(
+                    "'%s.%s' is not a callable." % (mod_name, func_name))
+    return lookup_view
+
+
+def get_mod_func(callback):
+    """
+    splits the string path to a class into a string path to the module
+    and the name of the class.
+
+    Examples
+    ========
+
+    >>> from sympy.utilities.source import get_mod_func
+    >>> get_mod_func('sympy.core.basic.Basic')
+    ('sympy.core.basic', 'Basic')
+
+    """
+    dot = callback.rfind('.')
+    if dot == -1:
+        return callback, ''
+    return callback[:dot], callback[dot + 1:]