fixed bugs in publication.py

input/publication.py

@@ -6,8 +6,8 @@ class Publication:
     """
     def __init__(self, doi_url: str, title: str
                  , contributors: str, journal: str
-                 , publication_date: str, subjects: list[str], num_citations: int = None
-                 , references: list[any] = None, citations: list[any] = None ):
+                 , publication_date: str, subjects = None, num_citations = None
+                 , references = None, citations = None ):
         """
         Parameters
         ----------
@@ -133,8 +133,8 @@ Subjects:''')
 
 class Citation:
     def __init__(self, doi_url: str, title: str
-                , journal: str, contributors: list[str]
-                , cit_type: str = "Citation"):
+                , journal: str, contributors = None
+                , cit_type = "Citation"):
         """
         Parameters
         ----------
@@ -168,7 +168,7 @@ class Citation:
 
 # This is just a replica of Citations 
 class Reference:
-    def __init__(self, doi_url: str, title: str, journal: str, contributors: list[str]):
+    def __init__(self, doi_url, title, journal, contributors):
         self.title = title
         self.doi_url = doi_url
         self.journal = journal