Readers: remove species default of None

Author: codingS3b

lib/python/picongpu/plugins/energy_histogram.py

@@ -100,7 +100,7 @@ def get_iterations(self, species, species_filter="all"):
                            delimiter=" ",
                            dtype=np.uint64).as_matrix()[:, 0]
 
-    def get(self, species=None, species_filter="all", iteration=None,
+    def get(self, species, species_filter="all", iteration=None,
             include_overflow=False, **kwargs):
         """
         Get a histogram.

lib/python/picongpu/plugins/phase_space.py

@@ -188,7 +188,7 @@ def get_iterations(self, species, species_filter='all', ps=None):
 
         return iterations
 
-    def get(self, species=None, species_filter='all', iteration=None, ps=None,
+    def get(self, species, species_filter='all', iteration=None, ps=None,
             **kwargs):
         """
         Get a phase space histogram.

lib/python/picongpu/plugins/png.py

@@ -154,7 +154,7 @@ def get_iterations(self, species, species_filter='all', axis=None,
 
         return sorted(iters)
 
-    def get(self, species=None, species_filter='all', iteration=None,
+    def get(self, species, species_filter='all', iteration=None,
             axis=None, slice_point=None, **kwargs):
         """
         Get an array representation of a PNG file.