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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 _set_typeahead(cls, el, value):
 """ Convert given `el` to typeahead input and set it to `value`. This method also sets the dropdown icons and descriptors. Args: el (obj):
 Element reference to the input you want to convert to typeahead. value (list):
 List of dicts with two keys: ``source`` and ``val``. """

        PlaceholderHandler.reset_placeholder_dropdown(el)

        # if there is no elements, show alert icon in glyph
        if not value and not el.value:
            DropdownHandler.set_dropdown_glyph(el.id, "glyphicon-alert")
            return

        # if there is only one element, don't use typeahead, just put the
        # information to the input, set different dropdown glyph and put source
        # to the dropdown
        if len(value) == 1:
            source = value[0]["source"].strip()
            dropdown_el = DropdownHandler.set_dropdown_glyph(
                el.id,
                "glyphicon-eye-open"
            )
            dropdown_content = "<span class='gray_text'>&nbsp;(%s)</span>"

            # save the source to the dropdown menu
            if source:
                dropdown_el.html = dropdown_content % source[::-1]

            el.value = value[0]["val"]
            return

        # get reference to parent element
        parent_id = el.parent.id
        if "typeahead" not in parent_id.lower():
            parent_id = el.parent.parent.id

        if parent_id in cls._set_by_typeahead:
            window.destroy_typeahead_tag("#" + parent_id)

        # if there are multiple elements, put them to the typeahead and show
        # dropdown glyph
        window.make_typeahead_tag("#" + parent_id, value)
        DropdownHandler.set_dropdown_glyph(el.id, "glyphicon-menu-down")
        PlaceholderHandler.set_placeholder_dropdown(el)
        cls._set_by_typeahead.add(parent_id)