Add 'volume' study to QuantFigure.studies

		Parameters:
			colorchange : bool
				If True then each volume bar will have a fill color 
				depending on if 'base' had a positive or negative
				change compared to the previous value
				If False then each volume bar will have a fill color 
				depending on if the volume data itself had a positive or negative
				change compared to the previous value
			column :string
				Defines the data column name that contains the volume data. 
				Default: 'volume'
			name : string
				Name given to the study
			str : string
				Label factory for studies
				The following wildcards can be used:
					{name} : Name of the column
					{study} : Name of the study
					{period} : Period used
				Examples:
					'study: {study} - period: {period}'
			
		kwargs : 
			base : string
				Defines the column which will define the
				positive/negative changes (if colorchange=True).
				Default = 'close'
			up_color : string
				Color for positive bars
			down_color : string
				Color for negative bars

def add_volume(self,colorchange=True,column=None,name='',str='{name}',**kwargs):
		"""
		Add 'volume' study to QuantFigure.studies

		Parameters:
			colorchange : bool
				If True then each volume bar will have a fill color 
				depending on if 'base' had a positive or negative
				change compared to the previous value
				If False then each volume bar will have a fill color 
				depending on if the volume data itself had a positive or negative
				change compared to the previous value
			column :string
				Defines the data column name that contains the volume data. 
				Default: 'volume'
			name : string
				Name given to the study
			str : string
				Label factory for studies
				The following wildcards can be used:
					{name} : Name of the column
					{study} : Name of the study
					{period} : Period used
				Examples:
					'study: {study} - period: {period}'
			
		kwargs : 
			base : string
				Defines the column which will define the
				positive/negative changes (if colorchange=True).
				Default = 'close'
			up_color : string
				Color for positive bars
			down_color : string
				Color for negative bars
		"""
		if not column:
			column=self._d['volume']
		up_color=kwargs.pop('up_color',self.theme['up_color'])
		down_color=kwargs.pop('down_color',self.theme['down_color'])
		study={'kind':'volume',
			   'name':name,
			   'params':{'colorchange':colorchange,'base':'close','column':column,
						 'str':None},
			  'display':utils.merge_dict({'up_color':up_color,'down_color':down_color},kwargs)}
		self._add_study(study)