Tidy up docstring

src/fk_graph/graph.py

@@ -67,7 +67,13 @@ def get_graph(
         primary_key: The primary key for the row.
         only_tables: (Optional) A list of table names. Any rows for tables not
           in the list will not be included in the graph.
-        exclude_edge: (Optional) A callable used to determine whether an edge will be included in the graph. It should be of the form `f(input_row, output_row) -> bool`, where the rows are SQL-Alchemy `Row` instances. The returned graph is always connected, so any nodes that can only be reached via the edge will also be omitted.
+        exclude_edge: (Optional) A callable used to determine whether an edge
+          will be included in the graph. It should be of the form
+          `f(input_row, output_row) -> bool`, where the rows are SQL-Alchemy
+          `Row` instances. If the function returns `True` for a given pair of
+          nodes, then the corresponding edge is not included in the graph. The
+          returned graph is always connected, so any nodes that can only be
+          reached via the edge will also be omitted.
 
     Raises:
         TableDoesNotExist - when the specified table does not exist.