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: null.m
    path of file: ./repos/chebfun/@chebop
    
    the code of the file until where you have to start completion: function v = null(N, prefs, nullity)
%NULL   Null space of a linear CHEBOP.
%   Z = NULL(N) returns a CHEBMATRIX with orthonormal columns which span the
%   null space of the linear CHEBOP N. That is, N(Z) has negligible elements,
%   SIZE(Z, 2) is the nullity of N, and Z'*Z = I. N may contain linear boundary
%   conditions, but they will be treated as homogeneous. The nullity is
%   determined by comparing the differential order of the system and the number
%   of supplied boundary conditions.
%
%   NULL(N, PREFS) allows additional preferences to be passed via the 
%   CHEBOPPREF, PREFS.
%
%   NULL(n, PREFS, K) or NULL(N, K) attempts to find K null vectors. If the
%   nullity of N is determined to be less than K then a warning is thrown. This
%   is useful in situations where the nullity is known in advance and the
%   algorithm struggles to determine it automatically.
%
%   Systems of equations are not yet supported.
%
% Example 1:
%   N = chebop(@(u) diff(u), [0, pi]);
%   V = null(N);
%   norm(N(V))
%
% Example 2:
%   N = chebop(@(x, u) 0.2*diff(u, 3) - sin(3*x).*diff(u));
%   N.rbc = 1;
%   V = null(N)
%   norm(N(V))
%   plot(V)
%
% See also CHEBOP/SVDS, CHEBOP/EIGS, NULL.

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

    
function v = null(N, prefs, nullity)
%NULL   Null space of a linear CHEBOP.
%   Z = NULL(N) returns a CHEBMATRIX with orthonormal columns which span the
%   null space of the linear CHEBOP N. That is, N(Z) has negligible elements,
%   SIZE(Z, 2) is the nullity of N, and Z'*Z = I. N may contain linear boundary
%   conditions, but they will be treated as homogeneous. The nullity is
%   determined by comparing the differential order of the system and the number
%   of supplied boundary conditions.
%
%   NULL(N, PREFS) allows additional preferences to be passed via the 
%   CHEBOPPREF, PREFS.
%
%   NULL(n, PREFS, K) or NULL(N, K) attempts to find K null vectors. If the
%   nullity of N is determined to be less than K then a warning is thrown. This
%   is useful in situations where the nullity is known in advance and the
%   algorithm struggles to determine it automatically.
%
%   Systems of equations are not yet supported.
%
% Example 1:
%   N = chebop(@(u) diff(u), [0, pi]);
%   V = null(N);
%   norm(N(V))
%
% Example 2:
%   N = chebop(@(x, u) 0.2*diff(u, 3) - sin(3*x).*diff(u));
%   N.rbc = 1;
%   V = null(N)
%   norm(N(V))
%   plot(V)
%
% See also CHEBOP/SVDS, CHEBOP/EIGS, NULL.

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

if ( nargin < 3 )
    nullity = [];
end