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/abc.py

@@ -0,0 +1,111 @@
+"""
+This module exports all latin and greek letters as Symbols, so you can
+conveniently do
+
+    >>> from sympy.abc import x, y
+
+instead of the slightly more clunky-looking
+
+    >>> from sympy import symbols
+    >>> x, y = symbols('x y')
+
+Caveats
+=======
+
+1. As of the time of writing this, the names ``O``, ``S``, ``I``, ``N``,
+``E``, and ``Q`` are colliding with names defined in SymPy. If you import them
+from both ``sympy.abc`` and ``sympy``, the second import will "win".
+This is an issue only for * imports, which should only be used for short-lived
+code such as interactive sessions and throwaway scripts that do not survive
+until the next SymPy upgrade, where ``sympy`` may contain a different set of
+names.
+
+2. This module does not define symbol names on demand, i.e.
+``from sympy.abc import foo`` will be reported as an error because
+``sympy.abc`` does not contain the name ``foo``. To get a symbol named ``foo``,
+you still need to use ``Symbol('foo')`` or ``symbols('foo')``.
+You can freely mix usage of ``sympy.abc`` and ``Symbol``/``symbols``, though
+sticking with one and only one way to get the symbols does tend to make the code
+more readable.
+
+The module also defines some special names to help detect which names clash
+with the default SymPy namespace.
+
+``_clash1`` defines all the single letter variables that clash with
+SymPy objects; ``_clash2`` defines the multi-letter clashing symbols;
+and ``_clash`` is the union of both. These can be passed for ``locals``
+during sympification if one desires Symbols rather than the non-Symbol
+objects for those names.
+
+Examples
+========
+
+>>> from sympy import S
+>>> from sympy.abc import _clash1, _clash2, _clash
+>>> S("Q & C", locals=_clash1)
+C & Q
+>>> S('pi(x)', locals=_clash2)
+pi(x)
+>>> S('pi(C, Q)', locals=_clash)
+pi(C, Q)
+
+"""
+from __future__ import annotations
+from typing import Any
+
+import string
+
+from .core import Symbol, symbols
+from .core.alphabets import greeks
+from sympy.parsing.sympy_parser import null
+
+##### Symbol definitions #####
+
+# Implementation note: The easiest way to avoid typos in the symbols()
+# parameter is to copy it from the left-hand side of the assignment.
+
+a, b, c, d, e, f, g, h, i, j = symbols('a, b, c, d, e, f, g, h, i, j')
+k, l, m, n, o, p, q, r, s, t = symbols('k, l, m, n, o, p, q, r, s, t')
+u, v, w, x, y, z = symbols('u, v, w, x, y, z')
+
+A, B, C, D, E, F, G, H, I, J = symbols('A, B, C, D, E, F, G, H, I, J')
+K, L, M, N, O, P, Q, R, S, T = symbols('K, L, M, N, O, P, Q, R, S, T')
+U, V, W, X, Y, Z = symbols('U, V, W, X, Y, Z')
+
+alpha, beta, gamma, delta = symbols('alpha, beta, gamma, delta')
+epsilon, zeta, eta, theta = symbols('epsilon, zeta, eta, theta')
+iota, kappa, lamda, mu = symbols('iota, kappa, lamda, mu')
+nu, xi, omicron, pi = symbols('nu, xi, omicron, pi')
+rho, sigma, tau, upsilon = symbols('rho, sigma, tau, upsilon')
+phi, chi, psi, omega = symbols('phi, chi, psi, omega')
+
+
+##### Clashing-symbols diagnostics #####
+
+# We want to know which names in SymPy collide with those in here.
+# This is mostly for diagnosing SymPy's namespace during SymPy development.
+
+_latin = list(string.ascii_letters)
+# QOSINE should not be imported as they clash; gamma, pi and zeta clash, too
+_greek = list(greeks) # make a copy, so we can mutate it
+# Note: We import lamda since lambda is a reserved keyword in Python
+_greek.remove("lambda")
+_greek.append("lamda")
+
+ns: dict[str, Any] = {}
+exec('from sympy import *', ns)
+_clash1: dict[str, Any] = {}
+_clash2: dict[str, Any] = {}
+while ns:
+    _k, _ = ns.popitem()
+    if _k in _greek:
+        _clash2[_k] = null
+        _greek.remove(_k)
+    elif _k in _latin:
+        _clash1[_k] = null
+        _latin.remove(_k)
+_clash = {}
+_clash.update(_clash1)
+_clash.update(_clash2)
+
+del _latin, _greek, Symbol, _k, null