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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _parse_value(self, html_data, field):
 """ Parse the HTML table to find the requested field's value. All of the values are passed in an HTML table row instead of as individual items. The values need to be parsed by matching the requested attribute with a parsing scheme that sports-reference uses to differentiate stats. This function returns a single value for the given attribute. Parameters html_data : string A string containing all of the rows of stats for a given team. If multiple tables are being referenced, this will be comprised of multiple rows in a single string. field : string The name of the attribute to match. Field must be a key in the PLAYER_SCHEME dictionary. Returns ------- list A list of all values that match the requested field. If no value could be found, returns None. """

        scheme = PLAYER_SCHEME[field]
        items = [i.text() for i in html_data(scheme).items()]
        # Stats can be added and removed on a yearly basis. If no stats are
        # found, return None and have that be the value.
        if len(items) == 0:
            return None
        return items