Add Constraints and Variables to Public API (#419)

Author: FBumann

linopy/__init__.py

@@ -14,15 +14,16 @@
 import linopy.monkey_patch_xarray  # noqa: F401
 from linopy.config import options
 from linopy.constants import EQUAL, GREATER_EQUAL, LESS_EQUAL
-from linopy.constraints import Constraint
+from linopy.constraints import Constraint, Constraints
 from linopy.expressions import LinearExpression, QuadraticExpression, merge
 from linopy.io import read_netcdf
-from linopy.model import Model, Variable, available_solvers
+from linopy.model import Model, Variable, Variables, available_solvers
 from linopy.objective import Objective
 from linopy.remote import RemoteHandler
 
 __all__ = (
     "Constraint",
+    "Constraints",
     "EQUAL",
     "GREATER_EQUAL",
     "LESS_EQUAL",
@@ -32,6 +33,7 @@
     "QuadraticExpression",
     "RemoteHandler",
     "Variable",
+    "Variables",
     "available_solvers",
     "merge",
     "options",