# in case of changes correct also the code in this method
self._re_exact_author_match=re.compile(r'\bexactauthor:(?P<author_name>.*?\b)(?= and | or | not |$)',re.IGNORECASE)
# regular expression that matches search term, its conent (words that
# are searched)and the operator preceding the term. In case that the
# names of the groups defined in the expression are changed, the
# chagned should be reflected in the code that use it.
self._re_search_term_pattern_match=re.compile(r'\b(?P<combine_operator>find|and|or|not)\s+(?P<search_term>title:|keyword:)(?P<search_content>.*?\b)(?= and | or | not |$)',re.IGNORECASE)
# regular expression used to split string by white space as separator