def insert_on(self, path, loc=None, replace=False):  # noqa: C901
        """Ensure self.location is on path

        If replace=False (default):
            - If location is already in path anywhere, do nothing.
            - Else:
              - If it's an egg and its parent directory is on path,
                insert just ahead of the parent.
              - Else: add to the end of path.
        If replace=True:
            - If location is already on path anywhere (not eggs)
              or higher priority than its parent (eggs)
              do nothing.
            - Else:
              - If it's an egg and its parent directory is on path,
                insert just ahead of the parent,
                removing any lower-priority entries.
              - Else: add it to the front of path.
        """

        loc = loc or self.location
        if not loc:
            return

        nloc = _normalize_cached(loc)
        bdir = os.path.dirname(nloc)
        npath = [(p and _normalize_cached(p) or p) for p in path]

        for p, item in enumerate(npath):
            if item == nloc:
                if replace:
                    break
                else:
                    # don't modify path (even removing duplicates) if
                    # found and not replace
                    return
            elif item == bdir and self.precedence == EGG_DIST:
                # if it's an .egg, give it precedence over its directory
                # UNLESS it's already been added to sys.path and replace=False
                if (not replace) and nloc in npath[p:]:
                    return
                if path is sys.path:
                    self.check_version_conflict()
                path.insert(p, loc)
                npath.insert(p, nloc)
                break
        else:
            if path is sys.path:
                self.check_version_conflict()
            if replace:
                path.insert(0, loc)
            else:
                path.append(loc)
            return

        # p is the spot where we found or inserted loc; now remove duplicates
        while True:
            try:
                np = npath.index(nloc, p + 1)
            except ValueError:
                break
            else:
                del npath[np], path[np]
                # ha!
                p = np

        return
Ensure self.location is on path

        If replace=False (default):
            - If location is already in path anywhere, do nothing.
            - Else:
              - If it's an egg and its parent directory is on path,
                insert just ahead of the parent.
              - Else: add to the end of path.
        If replace=True:
            - If location is already on path anywhere (not eggs)
              or higher priority than its parent (eggs)
              do nothing.
            - Else:
              - If it's an egg and its parent directory is on path,
                insert just ahead of the parent,
                removing any lower-priority entries.
              - Else: add it to the front of path.
        
src/pkg_resources/__init__.py