def direct_from_halo_catalog(**kwargs):
    """
    Function returns the concentrations that are already present
    in an input halo catalog.

    Parameters
    ----------
    table : object
        `~astropy.table.Table` storing halo catalog.

    concentration_key : string
        Name of the table column storing the concentration

    Returns
    -------
    concentration : array_like
        Concentrations of the input halos.
    """
    try:
        table = kwargs['table']
        concentration_key = kwargs['concentration_key']
    except KeyError:
        msg = """The ``direct_from_halo_catalog`` function accepts two keyword arguments:
``table`` and ``concentration_key``"""
        raise KeyError(msg)
    try:
        concentration = table[concentration_key]
    except:
        msg = """The ``{0}`` key does not appear in the input halo catalog.
However, you have selected the ``direct_from_halo_catalog`` option 
to model the concentration-mass relation.
The available keys are:

{1}
"""
        raise KeyError(msg.format(concentration_key, list(table.keys())))
    return concentration
