Merge branch 'master' into fix-plot-models-flux

source/MulensModel/modelparameters.py

@@ -673,17 +673,26 @@ def _check_valid_combination_1_source_xallarap(self, keys):
         if not self._type['xallarap']:
             return
 
-        required = ('xi_period xi_semimajor_axis xi_inclination '
-                    'xi_Omega_node xi_argument_of_latitude_reference').split()
+        self._check_orbit_parameters(keys, "xi_")
+
+    def _check_orbit_parameters(self, keys, prefix):
+        """
+        check if orbit is properly defined; prefix is added to
+        checked orbit parameters
+        """
+        required = ('period semimajor_axis inclination '
+                    'Omega_node argument_of_latitude_reference').split()
+        required = [prefix + req for req in required]
         for parameter in required:
             if parameter not in keys:
                 raise KeyError(parameter)
 
-        allowed = set(['xi_eccentricity', 'xi_omega_periapsis'])
+        allowed = set([prefix + 'eccentricity', prefix + 'omega_periapsis'])
         n_used = len(set(keys).intersection(allowed))
         if n_used not in [0, len(allowed)]:
             raise KeyError(
-                'Error in defining xi_eccentricity and xi_omega_periapsis. '
+                'Error in defining ' + prefix + 'eccentricity and ' +
+                prefix + 'omega_periapsis. ' +
                 'Both of them or neither should be defined.')
 
     def _check_valid_combination_1_source_Cassan08(self, keys):