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/unify/rewrite.py

@@ -0,0 +1,55 @@
+""" Functions to support rewriting of SymPy expressions """
+
+from sympy.core.expr import Expr
+from sympy.assumptions import ask
+from sympy.strategies.tools import subs
+from sympy.unify.usympy import rebuild, unify
+
+def rewriterule(source, target, variables=(), condition=None, assume=None):
+    """ Rewrite rule.
+
+    Transform expressions that match source into expressions that match target
+    treating all ``variables`` as wilds.
+
+    Examples
+    ========
+
+    >>> from sympy.abc import w, x, y, z
+    >>> from sympy.unify.rewrite import rewriterule
+    >>> from sympy import default_sort_key
+    >>> rl = rewriterule(x + y, x**y, [x, y])
+    >>> sorted(rl(z + 3), key=default_sort_key)
+    [3**z, z**3]
+
+    Use ``condition`` to specify additional requirements.  Inputs are taken in
+    the same order as is found in variables.
+
+    >>> rl = rewriterule(x + y, x**y, [x, y], lambda x, y: x.is_integer)
+    >>> list(rl(z + 3))
+    [3**z]
+
+    Use ``assume`` to specify additional requirements using new assumptions.
+
+    >>> from sympy.assumptions import Q
+    >>> rl = rewriterule(x + y, x**y, [x, y], assume=Q.integer(x))
+    >>> list(rl(z + 3))
+    [3**z]
+
+    Assumptions for the local context are provided at rule runtime
+
+    >>> list(rl(w + z, Q.integer(z)))
+    [z**w]
+    """
+
+    def rewrite_rl(expr, assumptions=True):
+        for match in unify(source, expr, {}, variables=variables):
+            if (condition and
+                not condition(*[match.get(var, var) for var in variables])):
+                continue
+            if (assume and not ask(assume.xreplace(match), assumptions)):
+                continue
+            expr2 = subs(match)(target)
+            if isinstance(expr2, Expr):
+                expr2 = rebuild(expr2)
+            yield expr2
+    return rewrite_rl