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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def national_significant_number(numobj):
 """Gets the national significant number of a phone number. Note that a national significant number doesn't contain a national prefix or any formatting. Arguments: numobj -- The PhoneNumber object for which the national significant number is needed. Returns the national significant number of the PhoneNumber object passed in. """

    # If leading zero(s) have been set, we prefix this now. Note this is not a
    # national prefix.
    national_number = U_EMPTY_STRING
    if numobj.italian_leading_zero:
        num_zeros = numobj.number_of_leading_zeros
        if num_zeros is None:
            num_zeros = 1
        if num_zeros > 0:
            national_number = U_ZERO * num_zeros
    national_number += str(numobj.national_number)
    return national_number