[docs]classNumberOfMentions(CountString):"""Determines the number of mentions in a string. Description: Given a list of strings, determine the number of mentions in each string. A mention is defined as a string that meets the following criteria: - Starts with a '@' character, followed by a sequence of alphanumeric characters - Present at the start of a string or after whitespace - Terminated by the end of the string, a whitespace, or a punctuation character other than '@' - e.g. The string '@yes-no' contains a valid mention ('@yes') - e.g. The string '@yes@' does not contain a valid mention This implementation handles Unicode characters. This implementation does not impose any character limit on mentions. If a string is missing, return `NaN`. Examples: >>> x = ['@user1 @user2', 'this is a string', '@@@__user1@1and_0@expression'] >>> number_of_mentions = NumberOfMentions() >>> number_of_mentions(x).tolist() [2.0, 0.0, 0.0] """name="number_of_mentions"input_types=[ColumnSchema(logical_type=NaturalLanguage)]return_type=ColumnSchema(logical_type=IntegerNullable,semantic_tags={"numeric"})default_value=0