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: MS_unwind_pm_90.m
    path of file: ./repos/MSAT/msat
    
    the code of the file until where you have to start completion: % MS_UNWIND_PM_90 - Unwind an angle until it is between -90 and 90 degrees
%
% // Part of MSAT - The Matlab Seismic Anisotropy Toolkit //
%
% Utility function to find the equivelent angle between -90 and 90 degrees
% assuming 180 defgree periodicity. 
%
%  % [angle] = unwind_pm_90(angle_in)
%
% Usage: 
%     for a given value of angle_in return a value greater than 
%     -90 and less than or equal to +90 by repetedly adding or subtracting
%     180. Angle can be a scalar or
    
function to find the equivelent angle between -90 and 90 degrees
% assuming 180 defgree periodicity. 
%
%  % [angle] = unwind_pm_90(angle_in)
%
% Usage: 
%     for a given value of angle_in return a value greater than 
%     -90 and less than or equal to +90 by repetedly adding or subtracting
%     180. Angle can be a scalar or a vector.

% Copyright (c) 2011, 2014 James Wookey and Andrew Walker
% All rights reserved.
% 
% Redistribution and use in source and binary forms, 
% with or without modification, are permitted provided 
% that the following conditions are met:
% 
%    * Redistributions of source code must retain the 
%      above copyright notice, this list of conditions 
%      and the following disclaimer.
%    * Redistributions in binary form must reproduce 
%      the above copyright notice, this list of conditions 
%      and the following disclaimer in the documentation 
%      and/or other materials provided with the distribution.
%    * Neither the name of the University of Bristol nor the names 
%      of its contributors may be used to end