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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 pem_to_der(cert, return_multiple=True):
 """ Converts a given certificate or list to PEM format"""


    # initialize the certificate array
    cert_list = []

    # If certificate is in DER then un-armour it
    if pem.detect(cert):
        for _, _, der_bytes in pem.unarmor(cert, multiple=True):
            cert_list.append(der_bytes)
    else:
        cert_list.append(cert)

    # return multiple if return_multiple is set else first element
    if return_multiple:
        return cert_list
    else:
        return cert_list.pop()