| mark_nucleus {tissue} | R Documentation | 
mark_nucleus(tissue,
    nucleus = ['#903ab5','#8826b1','#9026ae','#c23ec5'],
    tolerance = 13);a dataframe object that contains the nucleus pixel location 
 result, this result dataframe object contains at least two data 
 fields: x and y. such geometry pixel position could be used 
 for the downstream data analysis pipeline.