### Question:
DefaultAtlasSession implements AtlasInternalSession { @Override public AtlasFieldReader removeFieldReader(String docId) { if (docId == null || docId.isEmpty()) { return this.fieldReaderMap.remove(AtlasConstants.DEFAULT_SOURCE_DOCUMENT_ID); } return fieldReaderMap.remove(docId); } DefaultAtlasSession(DefaultAtlasContext context); @Override AtlasContext getAtlasContext(); @Override void setAtlasContext(AtlasContext atlasContext); @Override AtlasMapping getMapping(); @Override Validations getValidations(); @Override void setValidations(Validations validations); @Override Audits getAudits(); @Override void setAudits(Audits audits); @Override Object getDefaultSourceDocument(); @Override Object getSourceDocument(String docId); @Override boolean hasSourceDocument(String docId); @Override Map<String, Object> getSourceDocumentMap(); @Override Object getDefaultTargetDocument(); @Override Object getTargetDocument(String docId); @Override boolean hasTargetDocument(String docId); @Override Map<String, Object> getTargetDocumentMap(); @Override void setDefaultSourceDocument(Object sourceDoc); @Override void setSourceDocument(String docId, Object sourceDoc); @Override void setDefaultTargetDocument(Object targetDoc); @Override void setTargetDocument(String docId, Object targetDoc); @Override AtlasFieldReader getFieldReader(String docId); @Override T getFieldReader(String docId, Class<T> clazz); @Override void setFieldReader(String docId, AtlasFieldReader reader); @Override AtlasFieldReader removeFieldReader(String docId); @Override AtlasFieldWriter getFieldWriter(String docId); @Override T getFieldWriter(String docId, Class<T> clazz); @Override void setFieldWriter(String docId, AtlasFieldWriter writer); @Override AtlasFieldWriter removeFieldWriter(String docId); @Override Head head(); @Override @Deprecated Map<String, Object> getProperties(); @Override Map<String, Object> getSourceProperties(); @Override Map<String, Object> getTargetProperties(); @Override AtlasPropertyStrategy getAtlasPropertyStrategy(); @Override void setAtlasPropertyStrategy(AtlasPropertyStrategy strategy); @Override Integer errorCount(); @Override boolean hasErrors(); @Override boolean hasWarns(); @Override Integer warnCount();  }### Answer:
@Test public void testRemoveFieldReader() { session.removeFieldReader(null); session.removeFieldReader(""); session.removeFieldReader(AtlasConstants.DEFAULT_SOURCE_DOCUMENT_ID); }