def simplify_height(df):
	df['Body Height [cm]'] = df['Body Height [cm]'].fillna(-0.5)
	bins = (-1, 90, 100, 110, 120, 130, 140, etc....)
	group_names = ['Unknown', '90-100', '100-110', '110-120', '120-130', '130-140', etc....]
	df['Body Height [cm]'] = pd.cut(df['Body Height [cm]'], bins, labels=group_names)
	return df