Add get_beam_parse method in ArcEager, for Prodigy

spacy/syntax/arc_eager.pyx

@@ -390,6 +390,22 @@ cdef class ArcEager(TransitionSystem):
                 gold.c.labels[i] = self.strings.add(label)
         return gold
 
+    def get_beam_parses(self, Beam beam):
+        parses = []
+        probs = beam.probs
+        for i in range(beam.size):
+            state = <StateC*>beam.at(i)
+            if state.is_final():
+                self.finalize_state(state)
+                prob = probs[i]
+                parse = []
+                for j in range(state.length):
+                    head = state.H(j)
+                    label = self.strings[state._sent[j].dep]
+                    parse.append((head, j, label))
+                parses.append((prob, parse))
+        return parses
+
     cdef Transition lookup_transition(self, object name) except *:
         if '-' in name:
             move_str, label_str = name.split('-', 1)