docs: def parse_schema(schema_file):
          """
          parses the schema file and returns the columns that are later going to represent the columns of the genometric space dataframe
          :param schema_file: the path to the schema file
          :return: the columns of the schema file
          """
          e = xml.etree.ElementTree.parse(schema_file)
          root = e.getroot()
          cols = []
          for elem in root.findall(".//{http://genomic.elet.polimi.it/entities}field"):  # XPATH
              cols.append(elem.text)
          return cols