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/codegen/futils.py

@@ -0,0 +1,40 @@
+from itertools import chain
+from sympy.codegen.fnodes import Module
+from sympy.core.symbol import Dummy
+from sympy.printing.fortran import FCodePrinter
+
+""" This module collects utilities for rendering Fortran code. """
+
+
+def render_as_module(definitions, name, declarations=(), printer_settings=None):
+    """ Creates a ``Module`` instance and renders it as a string.
+
+    This generates Fortran source code for a module with the correct ``use`` statements.
+
+    Parameters
+    ==========
+
+    definitions : iterable
+        Passed to :class:`sympy.codegen.fnodes.Module`.
+    name : str
+        Passed to :class:`sympy.codegen.fnodes.Module`.
+    declarations : iterable
+        Passed to :class:`sympy.codegen.fnodes.Module`. It will be extended with
+        use statements, 'implicit none' and public list generated from ``definitions``.
+    printer_settings : dict
+        Passed to ``FCodePrinter`` (default: ``{'standard': 2003, 'source_format': 'free'}``).
+
+    """
+    printer_settings = printer_settings or {'standard': 2003, 'source_format': 'free'}
+    printer = FCodePrinter(printer_settings)
+    dummy = Dummy()
+    if isinstance(definitions, Module):
+        raise ValueError("This function expects to construct a module on its own.")
+    mod = Module(name, chain(declarations, [dummy]), definitions)
+    fstr = printer.doprint(mod)
+    module_use_str = '   %s\n' % '   \n'.join(['use %s, only: %s' % (k, ', '.join(v)) for
+                                                k, v in printer.module_uses.items()])
+    module_use_str += '   implicit none\n'
+    module_use_str += '   private\n'
+    module_use_str += '   public %s\n' % ', '.join([str(node.name) for node in definitions if getattr(node, 'name', None)])
+    return fstr.replace(printer.doprint(dummy), module_use_str)