Feature request: grammar / `WHERE` namespace extensions

Use case: Cypher supports a robust library for [datetime analysis](https://neo4j-contrib.github.io/neo4j-apoc-procedures/3.4/utilities/datetime-conversions/), among other extensions. While it is unrealistic to expect their integration here, it would be nice to allow python equivalents during queries. I envision something like this:

```python
import pandas as pd
GrandCypher(g, namespace={"datetime": pd.to_datetime, ...}).run("""
MATCH (a) --> (b)
WHERE a.date < datetime("2024-01-01")
RETURN a.name
""")
```

Would love to hear your thoughts.