def _create_source(foci, sample_sizes, space="MNI"):
    """Create dictionary according to nimads(ish) specification.

    .. versionadded:: 0.0.4

    Parameters
    ----------
    foci : :obj:`dict`
        A dictionary of foci in xyz (mm) coordinates whose keys represent
        different studies.
    sample_sizes : :obj:`list`
        The sample size for each study
    space : :obj:`str`
        The template space the coordinates are reported in. (Default='MNI')

    Returns
    -------
    source : :obj:`dict`
        study information in nimads format
    """
    source = {}
    for sample_size, (study, study_foci) in zip(sample_sizes, foci.items()):
        source[f"study-{study}"] = {
            "contrasts": {
                "1": {
                    "coords": {
                        "space": space,
                        "x": [c[0] for c in study_foci],
                        "y": [c[1] for c in study_foci],
                        "z": [c[2] for c in study_foci],
                    },
                    "metadata": {"sample_sizes": [sample_size]},
                }
            }
        }

    return source