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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 _add_form_fields(obj, lines):
 """Improve the documentation of a Django Form class. This highlights the available fields in the form. """

    lines.append("**Form fields:**")
    lines.append("")
    for name, field in obj.base_fields.items():
        field_type = "{}.{}".format(field.__class__.__module__, field.__class__.__name__)
        tpl = "* ``{name}``: {label} (:class:`~{field_type}`)"
        lines.append(tpl.format(
            name=name,
            field=field,
            label=field.label or name.replace('_', ' ').title(),
            field_type=field_type
        ))