Consider a best practice YAML output `flow_style`

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**Is your feature request related to a problem? Please describe.**

As explored during #18, by default PyYAML varies the chosen output form style:

> By default, PyYAML chooses the style of a collection depending on whether it has nested collections. If a collection has nested collections, it will be assigned the block style. Otherwise it will have the flow style.
>
> If you want collections to be always serialized in the block style, set the parameter default_flow_style of dump() to False. For instance,
>
>\>> print yaml.dump(yaml.load(document), default_flow_style=False)
>
> Source: [PyYaml Documentation](https://pyyaml.org/wiki/PyYAMLDocumentation)

The unpredictability of this default behaviour may make outputs harder to test.

**Describe the solution you'd like**

The working practices should be updated to recommend `yaml.dump` have `default_flow_style=False` passed. An issue could also be raised to make this uniform across the current code.

**Describe alternatives you've considered**

It's possible that `default_flow_style=True` defaults to always using a `flow` style of output. This didn't seem clear from the docs and wasn't tested thoroughly. But if the `flow` style is preferred this may be an approach. (See example of output below).

**Additional context**

YAML is written in with either the `flow` style or the `block` style.

Example: `flow` style:

```yml
{glossary: {GlossDiv: {GlossList: {GlossEntry: {Abbrev: 'ISO 8879:1986', Acronym: SGML,
GlossDef: {GlossSeeAlso: [GML, XML], para: 'A meta-markup language, used
to create markup languages such as DocBook.'}, GlossSee: markup, GlossTerm: Standard
Generalized Markup Language, ID: SGML, SortAs: SGML}}, title: S}, title: example
glossary}}
```

Example: `block` style

```yml
glossary:
GlossDiv:
GlossList:
GlossEntry:
Abbrev: ISO 8879:1986
Acronym: SGML
GlossDef:
GlossSeeAlso:
- GML
- XML
para: A meta-markup language, used to create markup languages such as DocBook.
GlossSee: markup
GlossTerm: Standard Generalized Markup Language
ID: SGML
SortAs: SGML
title: S
title: example glossary
```

Note also that the default behaviour seems to mix and match `flow` and `block` as in this section of default output:

```yml
Acronym: SGML
GlossDef:
GlossSeeAlso: [GML, XML]
para: A meta-markup language, used to create markup languages such as DocBook.
GlossSee: markup
```

No repository file is named. Find the working-practices documentation and review issue #18 alongside the PyYAML documentation linked here; update the guidance to recommend passing default_flow_style=False to yaml.dump, with the completed guidance making the preferred YAML output style explicit.

Written by the indexing model from the issue text.