code: def try_blas_flag(flags):
      from theano.gof.cmodule import GCC_compiler
  
      test_code = textwrap.dedent(
          """\
          extern "C" double ddot_(int*, double*, int*, double*, int*);
          int main(int argc, char** argv)
          {
              int Nx = 5;
              int Sx = 1;
              double x[5] = {0, 1, 2, 3, 4};
              double r = ddot_(&Nx, x, &Sx, x, &Sx);
  
              if ((r - 30.) > 1e-6 || (r - 30.) < -1e-6)
              {
                  return -1;
              }
              return 0;
          }
          """
      )
      cflags = list(flags)
      # to support path that includes spaces, we need to wrap it with double quotes on Windows
      path_wrapper = '"' if os.name == "nt" else ""
      cflags.extend(
          [
              "-L%s%s%s" % (path_wrapper, d, path_wrapper)
              for d in theano.gof.cmodule.std_lib_dirs()
          ]
      )
  
      res = GCC_compiler.try_compile_tmp(
          test_code, tmp_prefix="try_blas_", flags=cflags, try_run=True
      )
      # res[0]: shows successful compilation
      # res[1]: shows successful execution
      if res and res[0] and res[1]:
          return " ".join(flags)
      else:
          return ""
  
imports: from __future__ import absolute_import, print_function, division
  import errno
  import os
  import sys
  import logging
  import numpy
  import platform
  import textwrap
  import re
  import socket
  import struct
  import warnings
  from six import string_types
  import theano
  from theano.configparser import AddConfigVar, BoolParam, ConfigParam, EnumStr, FloatParam, IntParam, StrParam, TheanoConfigParser, THEANO_FLAGS_DICT
  from theano.misc.cpucount import cpuCount
  from theano.misc.windows import call_subprocess_Popen, output_subprocess_Popen
  from theano.compat import maybe_add_to_os_environ_pathlist
label_desc: Use image node_id 20 for calling a global function with example usage: try_blas_flag(flags) and returns: str, str