H5A_EXISTS_BY_NAME determines whether the attribute
attr_name exists on an object. That object is specified by its location and name,
obj_name , respectively.
loc_id specifies a location in the file containing the object.
obj_name is the name of the object to which the attribute is attached and can be a relative name, relative to
loc_id, or an absolute name, based in the root group of the file. If
loc_id fully specifies the object,
obj_name should be
'.' (a dot).
The link access property list,
lapl_id, may provide information regarding the properties of links required to access
obj_name. See “Link Access Properties” in the H5P APIs.