Function copy_value 

pub unsafe extern "C" fn copy_value(
    context: *mut c_context,
    value: *mut value,
    source: *const value,
) -> err

@brief Copy from another value @ingroup value_create @param[out] context Optional, stores error information @param[out] value Nix value to modify @param[in] source value to copy from @return error code, NIX_OK on success.