adding some utility functions which might be helpful for managing superevent IDs

gracedb/core/utils.py

+import string
+
+# Get lowercase alphabet as string
+ALPHABET = string.ascii_lowercase
+BASE = len(ALPHABET)
+
+def int_to_letters(num, positive_only=True):
+    """
+
+    Enumeration starts at 1 (i.e., 1 => 'a')
+    """
+
+    # Argument checking
+    if not isinstance(num, int):
+        raise TypeError("Input 'num' is not an int")
+    if (positive_only and num <= 0):
+        raise ValueError(("Input 'num' is non-positive, but the positive_only "
+            "flag is set"))
+
+    out_str = ''
+    while (num > BASE):
+        r = num % BASE
+        num /= BASE
+        out_str = ALPHABET[r-1] + out_str
+    out_str = ALPHABET[num-1] + out_str
+    return out_str
+
+def letters_to_int(letters):
+    # TODO: remove assert statement!
+    assert isinstance(letters, str), "letters is not a string"
+
+    letters = letters.lower()
+    pass