def verify_interval_info(in_dict):
    """Verifies post request was made with correct format

    The input dictionary must have the appropriate data keys
    and types, or be convertible to correct types, to be elicit
    the correct patient heart rate data.

    Args:
        in_dict (dict): input with patient ID and datetime

    Returns:
        str: if error, returns error message
        bool: if input verified, returns True
    """
    expected_keys = ("patient_id", "heart_rate_average_since")
    expected_types = (int, str)
    for i, key in enumerate(expected_keys):
        if key not in in_dict.keys():
            return "{} key not found".format(key)
        if type(in_dict[key]) is not expected_types[i]:
            if key == "patient_id":
                try:
                    in_dict[key] = int(in_dict[key])
                except ValueError:
                    return "{} value not correct type".format(key)
            else:
                return "{} value not correct type".format(key)
    return True