code: public static String getPrefix(String column) {
  		return column.contains( "." ) ? DOT_SEPARATOR_PATTERN.split( column )[0] : null;
  	}
docs: If the column name is a dotted column, returns the first part.
  Returns null otherwise.
  
  @param column the column that might have a prefix
  @return the first part of the prefix of the column or {@code null} if the column does not have a prefix.