Define writing style

It seems there are some inconsistencies in the cookbook's writing style.
For example:
* verb tense in titles: "Write a Parquet file" vs. "Reading a Parquet file"
* capitalization: "IPC" vs. "ipc", "parquet" vs. "Parquet", "numpy", "Arrow array" vs. "Arrow Array", etc.

Review the cookbook's existing titles and terminology, focusing on verb tense and capitalization examples such as “Write a Parquet file,” “IPC,” “numpy,” and “Arrow array.” Define consistent writing-style conventions and apply or document them across the cookbook; completion means the inconsistencies are resolved under an agreed style.

Written by the indexing model from the issue text.