AttributeError: 'ExecutionResult' object has no attribute 'splitlines'

[J G]

Here's an excerpt from the .robot file

*** Settings ***

Documentation A test suite...

| Library | Process |

| Library | Collections |

| Library | String |

*** Keywords ***

custom_tests

  [Documentation] Get firmware version

  ${result}= PerformTextReturningFunction custom_test1

  Log ${result}

  ${lines}=  Get Lines Containing String  ${result}  version*

The line above generates the following in the log

KEYWORD ${lines} = String . Get Lines Containing String ${result}, *

Documentation:

Returns lines of the given string that contain the pattern.

Start / End / Elapsed:
20220628 11:35:19.575 / 20220628 11:35:19.579 / 00:00:00.004
11:35:19.579
FAIL
AttributeError: 'ExecutionResult' object has no attribute 'splitlines'

I'm pretty much a newb at this, so what am I missing?