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: pr_getcmap.m
    path of file: ./repos/spm12/@slover/private
    
    the code of the file until where you have to start completion: function [cmap, warnstr] = pr_getcmap(acmapname)
% Get colormap of name acmapname

    
function [cmap, warnstr] = pr_getcmap(acmapname)
% Get colormap of name acmapname
% FORMAT [cmap, warnstr] = pr_getcmap(acmapname)
%
% Inputs
% acmapname   - string.  Can be (in order of precedence)
%               - matrix name in base workspace
%               - colour name; one of 'red','green','blue','cyan',
%                 'magenta', 'yellow', 'black', 'white'
%               - filename of .mat or .lut file.  If filename has no
%                 extension, assumes '.mat' extension
%
% Outputs
% cmap        - Nx3 colormap matrix
%               or empty if fails
% warnstr     - warning message if fails
%__________________________________________________________________________

% Matthew Brett
% $Id: pr_getcmap.m 6623 2015-12-03 18:38:08Z guillaume $

cmap = []; warnstr = [];
if nargin < 1
    acmapname = '';
end