@pimms.param<EOL><INDENT>def center(c):<DEDENT>
if c is None: return None<EOL>if not pimms.is_vector(c) or len(c) != <NUM_LIT:3>:<EOL><INDENT>raise ValueError('<STR_LIT>')<EOL><DEDENT>return pimms.imm_array(c)<EOL>
proj.center is the (x,y,z) coordinate of the center of the given projection on the sphere.