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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 _get_gdcmconv():
 """ Get the full path to gdcmconv. If not found raise error """

    gdcmconv_executable = settings.gdcmconv_path
    if gdcmconv_executable is None:
        gdcmconv_executable = _which('gdcmconv')
    if gdcmconv_executable is None:
        gdcmconv_executable = _which('gdcmconv.exe')

    if gdcmconv_executable is None:
        raise ConversionError('GDCMCONV_NOT_FOUND')

    return gdcmconv_executable