def get_boundary(content_type):
    """
    Extracts boundary from Content-Type
    """
    if content_type.startswith('multipart/form-data'):
        fields = content_type.split(';')
        for field in fields:
            k, sep, v = field.strip().partition('=')
            if k == 'boundary' and v:
                return v
        else:
            raise ValueError('multipart boundary not found')
