For a given meta-path and root node, when the meta-ath data.table is constructed, steps along
the meta-path with the same type (e.g., Author-Date-Author) are assigned the same column name.
Then, make.unique() is run to deduplicate column names by appending .1, .2, etc.
When querying the edge list (or neighbor list), the original (non-unique) type name is required.
Hence, this function strips the unique suffix from the type name (e.g., removes .1, .2, etc.).
clean_mp(type)Name of the type along any meta-path of interest.
Cleaned type name.