def _init_label_matrix(n_samples, n_classes):
    """Create and return zero matrix

    Parameters
    ----------
    n_samples : integer
        The number of nodes (samples) on the input graph
    n_classes : integer
        The number of classes (distinct labels) on the input graph

    Returns
    ----------
    F : numpy array, shape = [n_samples, n_classes]
        Label matrix
    """
    import numpy as np
    F = np.zeros((n_samples, n_classes))
    return F
