Fix from_json function to parse the specified schema

[shangyian]

Summary

The from_json function doesn't actually parse the specified schema correctly:

• It needs to strip out the beginning and end quotes
• There are two potential ways it can parse the schema, one for structs and one for arrays, both of which need to be handled here

Test Plan

Locally

• [ ] PR has an associated issue: #
• [ ] make check passes
• [ ] make test shows 100% unit test coverage

Deployment Plan

N/A

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