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: om_spher_mag_iso.m
    path of file: ./repos/fieldtrip/external/openmeeg
    
    the code of the file until where you have to start completion: function b=om_spher_mag_iso(x,q,p)
% Calculates the magnetic field (a vector) at point x on the surface of a layered
% conductive sphere induced by a current dipole of strength q at point
% p. The norm of x must be equal to the last rk, at least.
%
% All vectors (x,q,p) should be in 3D.
%
% Based on
% MOSHER & Al. : EEG and MEG: Forward solutions for inverse methods
% Ilmoniemi & Al
% Sarvas
% 
% Author: E. Olivi 2008/11/18

% Copyright (C) 2010-2017, OpenMEEG developers

mu0 = 4*pi*1e-7;
%mu0 = 1;


    
function b=om_spher_mag_iso(x,q,p)
% Calculates the magnetic field (a vector) at point x on the surface of a layered
% conductive sphere induced by a current dipole of strength q at point
% p. The norm of x must be equal to the last rk, at least.
%
% All vectors (x,q,p) should be in 3D.
%
% Based on
% MOSHER & Al. : EEG and MEG: Forward solutions for inverse methods
% Ilmoniemi & Al
% Sarvas
% 
% Author: E. Olivi 2008/11/18

% Copyright (C) 2010-2017, OpenMEEG developers

mu0 = 4*pi*1e-7;
%mu0 = 1;

[n,m] = size(x);
if m~=3,
  error('x should be a set of row 3D vectors.');
end