changed keyword arguments to mandatory arguments

classical/propagators.py

@@ -4,8 +4,8 @@ import numpy as np
 class Propagator:
     """ Base class for all propagators for classical particle dynamics """
     name = 'generic'
-    def __init__(self, syst=None, tstart=None, tend=None,
-                 tstep=None, substep=None, pbc=False, tqdm=False):
+    def __init__(self, syst, tstart, tend, tstep, substep=None, pbc=False,
+                 tqdm=False):
         self.q = syst.q0
         self.p = syst.p0
         self.q0 = syst.q0