logback-android/src/main/java/ch/qos/logback/core/joran/spi/InterpretationContext.java
public void addSubstitutionProperty(String key, String value) {
    if (key == null || value == null) {
      return;
    }
    // values with leading or trailing spaces are bad. We remove them now.
    value = value.trim();
    propertiesMap.put(key, value);
  }
public void addSubstitutionProperty(String key, String value) {
    if (key == null || value == null) {
      return;
    }
    // values with leading or trailing spaces are bad. We remove them now.
    value = value.trim();
    propertiesMap.put(key, value);
  }
Add a property to the properties of this execution context. If the property
exists already, it is overwritten.
@param key the property's key
@param value the value associated with the key