Fix a strange construct that seem unnecessary

And probably contribute to the circular import problem.

astroid/bases.py

@@ -316,9 +316,19 @@ def bool_value(self, context=None):
                 return True
         return result
 
-    # This is set in inference.py.
     def getitem(self, index, context=None):
-        pass
+        # TODO: Rewrap index to Const for this case
+        new_context = contextmod.bind_context_to_node(context, self)
+        if not context:
+            context = new_context
+        # Create a new CallContext for providing index as an argument.
+        new_context.callcontext = contextmod.CallContext(args=[index])
+        method = next(self.igetattr("__getitem__", context=context), None)
+        if not isinstance(method, BoundMethod):
+            raise exceptions.InferenceError(
+                "Could not find __getitem__ for {node!r}.", node=self, context=context
+            )
+        return next(method.infer_call_result(self, new_context))
 
 
 class UnboundMethod(Proxy):

astroid/builder.py

@@ -18,10 +18,10 @@
 The builder is not thread safe and can't be used to parse different sources
 at the same time.
 """
-
 import os
 import textwrap
 from tokenize import detect_encoding
+from typing import List, Union
 
 from astroid import (
     bases,
@@ -34,6 +34,7 @@
     util,
 )
 from astroid._ast import get_parser_module
+from astroid.node_classes import NodeNG
 
 objects = util.lazy_import("objects")
 
@@ -357,7 +358,7 @@ def _find_statement_by_line(node, line):
     return None
 
 
-def extract_node(code, module_name=""):
+def extract_node(code: str, module_name: str = "") -> Union[NodeNG, List[NodeNG]]:
     """Parses some Python code as a module and extracts a designated AST node.
 
     Statements:
@@ -409,7 +410,6 @@ def extract_node(code, module_name=""):
     a module. Will be passed through textwrap.dedent first.
     :param str module_name: The name of the module.
     :returns: The designated node from the parse tree, or a list of nodes.
-    :rtype: astroid.bases.NodeNG, or a list of nodes.
     """
 
     def _extract(node):

astroid/inference.py

@@ -872,28 +872,6 @@ def infer_index(self, context=None):
 
 nodes.Index._infer = infer_index
 
-# TODO: move directly into bases.Instance when the dependency hell
-# will be solved.
-def instance_getitem(self, index, context=None):
-    # Rewrap index to Const for this case
-    new_context = contextmod.bind_context_to_node(context, self)
-    if not context:
-        context = new_context
-
-    # Create a new callcontext for providing index as an argument.
-    new_context.callcontext = contextmod.CallContext(args=[index])
-
-    method = next(self.igetattr("__getitem__", context=context), None)
-    if not isinstance(method, bases.BoundMethod):
-        raise exceptions.InferenceError(
-            "Could not find __getitem__ for {node!r}.", node=self, context=context
-        )
-
-    return next(method.infer_call_result(self, new_context))
-
-
-bases.Instance.getitem = instance_getitem
-
 
 def _populate_context_lookup(call, context):
     # Allows context to be saved for later