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: clearPeriodicBCs.m
    path of file: ./repos/chebfun/@chebop
    
    the code of the file until where you have to start completion: function [N, L] = clearPeriodicBCs(N, L)
%CLEARPERIODICBCS    Clear periodic boundary conditions.
%   [N, L] = CLEARPERIODICBCS(N, L, PREF) clears N.BC, L.CONSTRAINT, and
%   L.CONTINUITY. This method only gets called if the current discretization in
%   use is TRIGCOLLOC, and is required since TRIGCOLLOC by construction will
%   only return periodic function as the solution, so there is no need to impose
%   periodic conditions on the discretized linear systems that arise.
%
% See also CHEBOP/DETERMINEDISCRETIZATION, CHEBOP/SOLVEBVP, CHEBOP/EIGS.

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

if ( isempty(N.bc) )
    % N.BC is empty already, so do nothing!
elseif ( isa(N.bc, 'char') && strcmpi(N.bc, 'periodic') )
    % Clear the conditions:

    
function [N, L] = clearPeriodicBCs(N, L)
%CLEARPERIODICBCS    Clear periodic boundary conditions.
%   [N, L] = CLEARPERIODICBCS(N, L, PREF) clears N.BC, L.CONSTRAINT, and
%   L.CONTINUITY. This method only gets called if the current discretization in
%   use is TRIGCOLLOC, and is required since TRIGCOLLOC by construction will
%   only return periodic function as the solution, so there is no need to impose
%   periodic conditions on the discretized linear systems that arise.
%
% See also CHEBOP/DETERMINEDISCRETIZATION, CHEBOP/SOLVEBVP, CHEBOP/EIGS.

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

if ( isempty(N.bc) )
    % N.BC is empty already, so do nothing!
elseif ( isa(N.bc, 'char') && strcmpi(N.bc, 'periodic') )
    % Clear the conditions:
    N.bc = [];
    L.constraint = [];
    L.continuity = [];
else
    error('CHEBFUN:CHEBOP:clearPeriodicBCs:nonperiodic', ...
        'TRIGCOLLOC only works with periodic boundary conditions.');
end