No need for coef function : complex(real, imag) already does the job

definition.py

@@ -19,14 +19,6 @@ class Plate:
         self.theta = theta
         self.orientation = orientation
 
-def coef(real, imag):
-    a = 0
-    if real != 0:
-        a = real
-    if imag != 0:
-        a+= imag*1j
-    return(a)
-
 class Photon:
     def __init__(self, state0, state1):
         self.state0 = [state0]