<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def toggleswitch() -> AnnData: """Simulated toggleswitch. Data obtained simulating a simple toggleswitch `Gardner *et al.*, Nature (2000) <https://doi.org/10.1038/35002131>`__. Simulate via :func:`~scanpy.api.sim`. Returns ------- Annotated data matrix. """

    filename = os.path.dirname(__file__) + '/toggleswitch.txt'
    adata = sc.read(filename, first_column_names=True)
    adata.uns['iroot'] = 0
    return adata