Fix language dispatch and result processing in Grafeo backend

[XXXM1R0XXX]

This pull request refactors and extends the GrafeoBackend class in src/anywidget_graph/backends/grafeo.py to improve support for multiple query languages and to better handle Grafeo-specific node and relationship formats. The main changes include adding language-specific execution logic, and introducing robust methods for processing Grafeo node and relationship dictionaries.

Language support enhancements:

• Added the _LANGUAGE_METHODS mapping to associate query languages (like "cypher", "gremlin", etc.) with their corresponding execution methods, enabling flexible query execution based on language.
• Updated the execute method to use the appropriate database method for the specified language, falling back to a generic execute if no match is found.

Grafeo node and relationship processing improvements:

• Refactored _process_result to prioritize Grafeo node and relationship detection using new helper methods, ensuring correct conversion to widget formats.
• Added static methods _is_grafeo_node, _is_grafeo_relationship, _grafeo_node_to_dict, and _grafeo_relationship_to_dict to reliably identify and transform Grafeo node and relationship dictionaries for downstream use.

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Simplified API Usage Examples

Thanks to these improvements, you no longer need to manually parse raw results using internal private methods (like _process_result). You can now easily render a Grafeo graph using one of the following simplified approaches:

Setup data:

from grafeo import GrafeoDB
from anywidget_graph import Graph

db = GrafeoDB()

# Create people
alix = db.create_node(["Person"], {"name": "Alix", "age": 30, "city": "Utrecht"})
gus = db.create_node(["Person"], {"name": "Gus", "age": 35, "city": "Portland"})
harm = db.create_node(["Person"], {"name": "Harm", "age": 28, "city": "Utrecht"})
dave = db.create_node(["Person"], {"name": "Dave", "age": 40, "city": "San Francisco"})
eve = db.create_node(["Person"], {"name": "Eve", "age": 32, "city": "Portland"})

# Create companies
acme = db.create_node(["Company"], {"name": "Acme Corp", "industry": "Tech"})
globex = db.create_node(["Company"], {"name": "Globex Inc", "industry": "Finance"})

# Friendships
db.create_edge(alix.id, gus.id, "KNOWS", {"since": 2020})
db.create_edge(alix.id, harm.id, "KNOWS", {"since": 2019})
db.create_edge(gus.id, harm.id, "KNOWS", {"since": 2021})
db.create_edge(gus.id, dave.id, "KNOWS", {"since": 2018})
db.create_edge(harm.id, eve.id, "KNOWS", {"since": 2022})
db.create_edge(dave.id, eve.id, "KNOWS", {"since": 2020})

# Employment
db.create_edge(alix.id, acme.id, "WORKS_AT", {"role": "Engineer"})
db.create_edge(gus.id, acme.id, "WORKS_AT", {"role": "Manager"})
db.create_edge(harm.id, globex.id, "WORKS_AT", {"role": "Analyst"})
db.create_edge(dave.id, globex.id, "WORKS_AT", {"role": "Director"})
db.create_edge(eve.id, acme.id, "WORKS_AT", {"role": "Designer"})

graph = Graph(database_backend="grafeo", grafeo_db=db)

Option 1: Using Widget Properties (Recommended)
The widget can now natively parse the query using the assigned query language.

# Programmatically execute the query to extract the graph
graph.query = "MATCH (n)-[r]->(m) RETURN n, r, m"
graph.query_language = "cypher"

# Render
graph

Option 2: Using the Backend Execute Method directly
The execute method now properly respects the language parameter and correctly formats the output out-of-the-box.

# Fetch and format nodes and edges directly from the backend
nodes, edges = graph.backend.execute("MATCH (n)-[r]->(m) RETURN n, r, m", language="cypher")

# Assign to widget
graph.nodes = nodes
graph.edges = edges

# Render
graph

[StevenBtw]

Thanks for this contribution @XXXM1R0XXX! I have just incorporated your changes
into the 0.2.8 release with a few additions (ClassVar lint fix, test
coverage). Your Co-Authored-By credit is on the commit.

Closing in favor of the release branch, which includes your work.