remove incorrect input from Constant nodes

Author: jmitrevs

hls4ml/model/layers.py

@@ -357,7 +357,7 @@ def initialize(self):
 
 
 class Constant(Layer):
-    # one could consider making this a weight attribute, but given it's transient nature, I am not sure it helps
+    # one could consider making this a weight attribute, but given its transient nature, I am not sure it helps
     _expected_attributes = [
         Attribute('value', value_type=np.ndarray),
     ]
@@ -371,6 +371,10 @@ def initialize(self):
         dims = [f'{self.name}_{i}' for i in range(len(shape))]
         quantizer = self.get_attr('quantizer')
 
+        # the graph._make_graph function sets the input node to the previous node
+        # if it is not set. That is incorrect for Constant nodes, so remove the input node
+        self.inputs = []
+
         # Should the else clause below be None or UnspecifiedPrecisionType
         precision = quantizer.hls_type if quantizer is not None else UnspecifiedPrecisionType()