<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def install_as_gi():
 """Call before the first gi import to redirect gi imports to pgi"""


    import sys

    # check if gi has already been replaces
    if "gi.repository" in const.PREFIX:
        return

    # make sure gi isn't loaded first
    for mod in iterkeys(sys.modules):
        if mod == "gi" or mod.startswith("gi."):
            raise AssertionError("pgi has to be imported before gi")

    # replace and tell the import hook
    import pgi
    import pgi.repository
    sys.modules["gi"] = pgi
    sys.modules["gi.repository"] = pgi.repository
    const.PREFIX.append("gi.repository")