[HANDS-ON BUG] Minor capitalization bug that invalidates choice.

**Describe the bug**
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Located in Unit 2.1 Building Agents That Use Code
Minor capitalization bug that invalidates "futuristic Gotham" choice in SuperheroPartyThemeTool.

**To Reproduce**
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If you prompt the agent with "futuristic Gotham" theme, you would get response that the theme party idea is not found.
**Screenshots**
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**Additional context**
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Change the key in themes from `futuristic Gotham` to `futuristic gotham`