You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: ex_axistressstrain2.m
    path of file: ./repos/featool-multiphysics/examples
    
    the code of the file until where you have to start completion: function [ fea, out ] = ex_axistressstrain2( varargin )
%EX_AXISTRESSSTRAIN2 Example for a pressurized hollow sphere axisymmetric stress-strain.
%
%   [ FEA, OUT ] = EX_AXISTRESSSTRAIN2( VARARGIN ) Example to calculate displacements and stresses
%   in a pressurized hollow sphere in axisymmetric/cylindrical coordinates.
%
%   Ref. 4.1.4 Pressurized hollow sphere.
%   [1] Applied Mechanics of Solids, Allan F. Bower, 2012 (http://solidmechanics.org/).
%
%   Accepts the following property/value pairs.
%
%       Input       Value/{Default}        Description
%       -----------------------------------------------------------------------------------
%       a           scalar {1}             Cylinder inner radius
%       b           scalar {2}             Cylinder outer radius
%       p           scalar {20e4}          Load force
%       E           scalar {200e9}         Modulus of elasticity
%       nu          scalar {0.3}           Poissons ratio
%       igrid       scalar 0/{<0}          Cell type (0=quadrilaterals, <0=triangles)
%       sfun        string {sflag2}        Shape function for displacements
%       iplot       scalar 0/{1}           Plot solution (=1)
%                                                                                         .
%       Output      Value/(Size)           Description
%       -----------------------------------------------------------------------------------
%       fea         struct                 Problem definition struct
%       out         struct                 Output struct

% Copyright 2013-2023 Precise Simulation, Ltd.

    
function [ fea, out ] = ex_axistressstrain2( varargin )
%EX_AXISTRESSSTRAIN2 Example for a pressurized hollow sphere axisymmetric stress-strain.
%
%   [ FEA, OUT ] = EX_AXISTRESSSTRAIN2( VARARGIN ) Example to calculate displacements and stresses
%   in a pressurized hollow sphere in axisymmetric/cylindrical coordinates.
%
%   Ref. 4.1.4 Pressurized hollow sphere.
%   [1] Applied Mechanics of Solids, Allan F. Bower, 2012 (http://solidmechanics.org/).
%
%   Accepts the following property/value pairs.
%
%       Input       Value/{Default}        Description
%       -----------------------------------------------------------------------------------
%       a           scalar {1}             Cylinder inner radius
%       b           scalar {2}             Cylinder outer radius
%       p           scalar {20e4}          Load force
%       E           scalar {200e9}         Modulus of elasticity
%       nu          scalar {0.3}           Poissons ratio
%       igrid       scalar 0/{<0}          Cell type (0=quadrilaterals, <0=triangles)
%       sfun        string {sflag2}        Shape function for displacements
%       iplot       scalar 0/{1}           Plot solution (=1)
%                                                                                         .
%       Output      Value/(Size)           Description
%       -----------------------------------------------------------------------------------
%       fea         struct                 Problem definition struct
%       out         struct                 Output struct

% Copyright 2013-2023 Precise Simulation, Ltd.


cOptDef = { 'a',        1;
            'b',        2;
            'p',        20e4;
            'E',        200e9;
            'nu',       0.3;
            'igrid',    0;
            'sfun',     'sflag2';
            'iplot',    1;
            'tol',      5e-3;
            'fid',      1 };
[got,opt] = parseopt(cOptDef,varargin{:});
fid       = opt.fid;


% Geometry and grid.
a = opt.a;
b = opt.b;
if ( opt.igrid==1 )
  error('ex_axistressstrain2: unstructured grid not supported.')
else
  fea.grid = ringgrid( 12, 72, a, b );
  fea.grid = delcells( fea.grid, selcells( fea.grid, '(x<=eps) | (y<=eps)') );
  if( opt.igrid<0 )
    fea.grid = quad2tri( fea.grid );
  end