Returns dictionary of some basic features that can be calculated for segmented time
    series data

def base_features():
    ''' Returns dictionary of some basic features that can be calculated for segmented time
    series data '''
    features = {'mean': mean,
                'median': median,
                'abs_energy': abs_energy,
                'std': std,
                'var': var,
                'min': minimum,
                'max': maximum,
                'skew': skew,
                'kurt': kurt,
                'mse': mse,
                'mnx': mean_crossings}
    return features