refactor: remove support for sqlalchemy connections (psycopg2 driver …

…only)

README.md

@@ -126,30 +126,9 @@ split_features = split_by_sql(
 
 - The db parameter can be a connection string to start a new connection.
 - Or an existing database connection can be reused.
-- To do this, either the psycopg2 connection, or a SQLAlchemy Session
+- To do this, either the psycopg2 connection, or a DBAPI connection string
   must be passed:
 
-SQLAlchemy example:
-
-```python
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker
-from fmtm_splitter.splitter import split_by_sql
-
-# Creates a SQLAlchemy Session object
-engine = create_engine("postgresql://postgres:postgres@localhost/postgres")
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-db = SessionLocal()
-
-# Then pass this object as the db param
-split_features = split_by_sql(
-    aoi,
-    db,
-    num_buildings=50,
-    osm_extract=osm_extracts,
-)
-```
-
 psycopg2 example:
 
 ```python

fmtm_splitter/db.py

@@ -24,13 +24,6 @@
 from psycopg2.extras import Json, register_uuid
 from shapely.geometry import Polygon
 
-try:
-    import sqlalchemy
-
-    _sqlalchemy_import = True
-except ImportError:
-    _sqlalchemy_import = False
-
 log = logging.getLogger(__name__)
 
 
@@ -40,12 +33,10 @@ def create_connection(
     """Get db connection from existing psycopg2 connection, or URL string.
 
     Args:
-        db (str, psycopg2.extensions.connection, sqlalchemy.orm.session.Session):
+        db (str, psycopg2.extensions.connection):
             string or existing db connection.
             If `db` is a string, a new connection is generated.
             If `db` is a psycopg2 connection, the connection is re-used.
-            If `db` is a sqlalchemy.orm.session.Session object, the connection
-                is also reused.
 
     Returns:
         conn: DBAPI connection object to generate cursors from.
@@ -58,13 +49,8 @@ def create_connection(
         conn = db
     elif isinstance(db, str):
         conn = psycopg2.connect(db)
-    elif _sqlalchemy_import and isinstance(db, sqlalchemy.orm.session.Session):
-        conn = db.connection().connection
     else:
-        msg = (
-            "The `db` variable is not a valid string, psycopg2 connection, "
-            "or SQLAlchemy Session."
-        )
+        msg = "The `db` variable is not a valid string or psycopg2 connection."
         log.error(msg)
         raise ValueError(msg)