Move all imports to top of file

A few months ago I had an issue setting up mocking because I was
trying to be clever importing these libraries only when I needed
them rather than at the global scope. Someone pointed out to me
that if the imports are at the top of the file Falcon will load
them once when the WSGI server starts, whereas if they are in the
on_get() or on_post() they will load for every request! Also, it
seems that PEP8 recommends keeping imports at the top of the file
anyways, so I will just do that.

Imports sorted with isort.

See: https://www.python.org/dev/peps/pep-0008/#imports

dspace_statistics_api/app.py

@@ -1,4 +1,5 @@
 import falcon
+import psycopg2.extras
 
 from .database import DatabaseManager
 from .items import get_downloads, get_views
@@ -120,8 +121,6 @@ class ItemResource:
     def on_get(self, req, resp, item_id):
         """Handles GET requests"""
 
-        import psycopg2.extras
-
         # Adapt Python’s uuid.UUID type to PostgreSQL’s uuid
         # See: https://www.psycopg.org/docs/extras.html
         psycopg2.extras.register_uuid()

dspace_statistics_api/items.py

@@ -1,6 +1,7 @@
 import requests
 
 from .config import SOLR_SERVER
+from .util import get_statistics_shards
 
 
 def get_views(solr_date_string: str, items: list):
@@ -11,7 +12,6 @@ def get_views(solr_date_string: str, items: list):
     :parameter items (list): a list of item IDs
     :returns: A dict of item IDs and views
     """
-    from .util import get_statistics_shards
     shards = get_statistics_shards()
 
     # Join the UUIDs with "OR" and escape the hyphens for Solr
@@ -62,7 +62,6 @@ def get_downloads(solr_date_string: str, items: list):
     :parameter items (list): a list of item IDs
     :returns: A dict of item IDs and downloads
     """
-    from .util import get_statistics_shards
     shards = get_statistics_shards()
 
     # Join the UUIDs with "OR" and escape the hyphens for Solr

dspace_statistics_api/util.py

@@ -1,4 +1,11 @@
+import datetime
+import json
+import re
+
 import falcon
+import requests
+
+from .config import SOLR_SERVER
 
 
 def get_statistics_shards():
@@ -8,11 +15,6 @@ def get_statistics_shards():
     Returns:
         str:A list of Solr statistics shards separated by commas.
     """
-    import re
-
-    import requests
-
-    from .config import SOLR_SERVER
 
     # Initialize an empty list for statistics core years
     statistics_core_years = []
@@ -58,7 +60,6 @@ def get_statistics_shards():
 
 
 def is_valid_date(date):
-    import datetime
 
     try:
         # Solr date format is: 2020-01-01T00:00:00Z
@@ -78,7 +79,6 @@ def validate_items_post_parameters(req, resp, resource, params):
 
     Meant to be used as a `before` hook.
     """
-    import json
 
     # Only attempt to read the POSTed request if its length is not 0 (or
     # rather, in the Python sense, if length is not a False-y value).