code: def get_string(
      dump_fn, routines, prefix="file", header=False, empty=False
  ):
      """Wrapper for dump_fn. dump_fn writes its results to a stream object and
      this wrapper returns the contents of that stream as a string. This
      auxiliary function is used by many tests below.
  
      The header and the empty lines are not generated to facilitate the
      testing of the output.
      """
      output = StringIO()
      dump_fn(routines, output, prefix, header, empty)
      source = output.getvalue()
      output.close()
      return source
  
imports: from io import StringIO
  from sympy.core import symbols, Eq, pi, Catalan, Lambda, Dummy
  from sympy.core.relational import Equality
  from sympy.core.symbol import Symbol
  from sympy.functions.special.error_functions import erf
  from sympy.integrals.integrals import Integral
  from sympy.matrices import Matrix, MatrixSymbol
  from sympy.utilities.codegen import codegen, make_routine, CCodeGen, C89CodeGen, C99CodeGen, InputArgument, CodeGenError, FCodeGen, CodeGenArgumentListError, OutputArgument, InOutArgument
  from sympy.testing.pytest import raises
  from sympy.utilities.lambdify import implemented_function
label_desc: Use image node_id 1 for calling a global function with example usage: get_string(dump_fn, routines, prefix, header, empty) and returns: source