<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def __prepare_histogram(h1, h2):
 """Convert the histograms to scipy.ndarrays if required."""

    h1 = h1 if scipy.ndarray == type(h1) else scipy.asarray(h1)
    h2 = h2 if scipy.ndarray == type(h2) else scipy.asarray(h2)
    if h1.shape != h2.shape or h1.size != h2.size:
        raise ValueError('h1 and h2 must be of same shape and size')
    return h1, h2