Add dictionary in the belief and actions associated with it

[20001LastOrder]

Description

Add a dictionary in the belief that can be modified and retrieved by an agent. The keys can be nested by dot notations.

Add directions for contributors. For example, do developers need to run poetry install after picking up these changes?
poetry install is needed since a new library pydash is introduced to manage nested dictionaries

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Maintenance
• New release

Related issues

Closed #405

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[Eyobyb]

is there any particular reason we want the get_all_keys function is nested rather than taking it out since there is no other time its being called inside ?