import json


def sqlalchemy_object_to_json(obj):
    """Convert a SQLAlchemy object (such as a Platform instance) to a JSON string

    :param obj: SQLAlchemy object
    :type obj: obj
    :return: JSON string containing values of all columns
    :rtype: str
    """
    columns = obj.__table__.columns

    output_dict = {}

    for col in columns:
        output_dict[col.name] = str(getattr(obj, col.name))

    return json.dumps(output_dict)