Get information about EUtils databasesSource:
Gather information about EUtils generally, or a given Eutils database.
Note: The most common uses-cases for the einfo util are finding the list of
search fields available for a given database or the other NCBI databases to
which records in a given database might be linked. Both these use cases
are implemented in higher-level functions that return just this information
Consequently most users will not have a reason to use this function (though
it is exported by
rentrez for the sake of completeness.
character database about which to retrieve information (optional)
config vector passed on to
XMLInternalDocument with information describing either all the databases available in Eutils (if db is not set) or one particular database (set by 'db')