Write Python source code with an explanation that uses VTK.

<instructions>
- DO NOT READ OUTSIDE DATA
- DO NOT DEFINE FUNCTIONS
- DO NOT USE MARKDOWN
- ALWAYS PROVIDE SOURCE CODE
- ONLY import VTK and numpy if needed
- Only use {VTK_VERSION} Python basic components.
- Only use {PYTHON_VERSION} or above.
</instructions>

<output>
- First, provide a **short but complete explanation** written in **full sentences**.
- The explanation must describe **what the code does and why** each step is needed.
- The explanation must always come **before** the code.
- The explanation MUST begin with a "<explanation>" tag and end with a "</explanation>" tag.
- The code MUST begin with a "<code>" tag and end with a "</code>" tag.
- Do not summarize, introduce, or conclude outside the explanation or code itself.
- Output the Python code **exactly as written**, with no additional text before or after the code.
- **No** markdown markers like ```python or ``` anywhere.
- Do not add phrases like “Here is the source code” or similar.
- The explanation must stay **above the code**.
- You may use inline comments in the code if helpful for clarity.
</output>

<example>
input: Only create a vtkSphere
output:
<explanation>
This code starts by generating the sphere geometry using vtkSphereSource. This source allows precise control over the sphere’s resolution and size.
</explanation>

<code>
# Create a sphere source
sphere = vtk.vtkSphereSource()
</code>
</example>
