def construct_api_params(
        business_unit=None,
        event_type=None,
        limit=None,
        page_token=None
):
    """
    Constructs the parameters object for the API call. Note that startDateUtc and
    endDateUtc are not listed here (although they are parameters); this is because
    they are included already in the URL

    Args:
        business_unit (str): Comma separated list of business unit IDs
        event_type (str): Comma separated list of event types.
                          Allowed event types are: ON_PREM_EXPOSURE_APPEARANCE,ON_PREM_EXPOSURE_DISAPPEARANCE,
                          ON_PREM_EXPOSURE_REAPPEARANCE. Beta event types are: CLOUD_EXPOSURE_APPEARANCE,
                          CLOUD_EXPOSURE_DISAPPEARANCE,CLOUD_EXPOSURE_REAPPEARANCE
        limit (int): Number of events to be fetched per page of results. Max and default value is 10,000
        page_token (str): Page token of page
    Returns:
         dict: the params object to be sent to the API
    """
    tokens = {
        'businessUnit': business_unit,
        'eventType': event_type,
        'limit': limit,
        'pageToken': page_token
    }
    params = {}

    for token_key, token_value in tokens.items():
        if token_value is not None:
            params.update({token_key: token_value})

    return params