'Appends a new column of data to the data source.
Args:
data (seq) : new data to add
name (str, optional) : column name to use.
If not supplied, generate a name of the form "Series ####"
Returns:
str:  the column name used'

def add(self, data, name=None):

    if (name is None):
        n = len(self.data)
        while (('Series    %d' % n) in self.data):
            n += 1
        name = ('Series    %d' % n)
    self.column_names.append(name)
    self.data[name] = data
    return name
