Added avg query

src/cpl_query/_query/avg_query.py

@@ -0,0 +1,22 @@
+from typing import Callable, Union
+
+from cpl_query.exceptions import InvalidTypeException, WrongTypeException
+from cpl_query.extension.iterable_abc import IterableABC
+
+
+def avg_query(_list: IterableABC, _t: type, _func: Callable) -> Union[int, float, complex]:
+    average = 0
+    count = len(_list)
+
+    if _t != int and _t != float and _t != complex:
+        raise InvalidTypeException()
+
+    for element in _list:
+        value = _func(element)
+        if type(value) != _t:
+            raise WrongTypeException()
+
+        average += value
+
+    return average / count
+