'take a lookup plugin name and store it correctly'

def _preprocess_loop(self, ds, new_ds, k, v):

    loop_name = k.replace('with_', '')
    if (new_ds.get('loop') is not None):
        raise AnsibleError(('duplicate    loop    in    task:    %s' % loop_name), obj=ds)
    if (v is None):
        raise AnsibleError(('you    must    specify    a    value    when    using    %s' % k), obj=ds)
    new_ds['loop'] = loop_name
    new_ds['loop_args'] = v
