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: solvepde.m
    path of file: ./repos/chebfun/@spinoperator
    
    the code of the file until where you have to start completion:     function [uOut, tOut, computingTime] = solvepde(vararg
    
function [uOut, tOut, computingTime] = solvepde(varargin)
%SOLVEPDE   Solve a PDE defined by a SPINOP, SPINOP2, SPINOP3 or SPINOPSPHERE.
%   SOLVEPDE is called by SPIN, SPIN2, SPIN3 and SPINSPHERE. It is not called
%   directly by the user. Appropriate help texts can be found in SPIN, SPIN2,
%   SPIN3 and SPINSPHERE.
%
% See also SPIN, SPIN2, SPIN3, SPINSPHERE.

% Copyright 2017 by The University of Oxford and The Chebfun Developers.
% See http://www.chebfun.org/ for Chebfun information.

%% Parse inputs:

% SOLVEPDE has been called by SPIN/SPIN2/SPIN3/SPINSPHERE. The inputs have been 
% parsed in those files and are expeceted to be:
%
% OPTION 1.     SOLVEPDE(S, N, DT), S is a SPINOPERATOR object, N is the number
%               of grid points and DT is the time-step.
%
% OPTION 2.     SOLVEPDE(S, N, DT, PREF), PREF is a SPINPREFERENCE.

% Get the inputs:
if ( nargin == 3 ) % OPTION 1
    S = varargin{1};
    N = varargin{2};
    dt = varargin{3};
    pref = getPreference(S); % get the default preferences
elseif ( nargin == 4 ) % OPTION 2
    S = varargin{1};
    N = varargin{2};
    dt = varargin{3};
    pref = varargin{4};
end