public class soapSforceComSchemasClassAccountins {
 public class SessionHeader_element {
        public String x00D90000000y0lh_AQ0AQGIsi542TCnp_73StsP8nawV5_7uVrHfVM0SyclcA_h1XKIVMRIiQAFjveUkYoo0HcVFXVHV1J6vjgM92eC2mdTmQCWQ;
        private String[] x00D90000000y0lh_AQ0AQGIsi542TCnp_73StsP8nawV5_7uVrHfVM0SyclcA_h1XKIVMRIiQAFjveUkYoo0HcVFXVHV1J6vjgM92eC2mdTmQCWQ_type_info = new String[]{'00D90000000y0lh!AQ0AQGIsi542TCnp.73StsP8nawV5.7uVrHfVM0SyclcA.h1XKIVMRIiQAFjveUkYoo0HcVFXVHV1J6vjgM92eC2mdTmQCWQ','http://soap.sforce.com/schemas/class/AccountInsert',null,'1','1','false'};
        private String[] apex_schema_type_info = new String[]{'http://soap.sforce.com/schemas/class/AccountInsert','true','false'};
        private String[] field_order_type_info = new String[]{'x00D90000000y0lh_AQ0AQGIsi542TCnp_73StsP8nawV5_7uVrHfVM0SyclcA_h1XKIVMRIiQAFjveUkYoo0HcVFXVHV1J6vjgM92eC2mdTmQCWQ'};
    }
    public class DebuggingInfo_element {
        public String debugLog;
        private String[] debugLog_type_info = new String[]{'debugLog','http://soap.sforce.com/schemas/class/AccountInsert',null,'1','1','false'};
        private String[] apex_schema_type_info = new String[]{'http://soap.sforce.com/schemas/class/AccountInsert','true','false'};
        private String[] field_order_type_info = new String[]{'debugLog'};
    }
    public class AccountInsert {
        public String endpoint_x = 'https://ap1.salesforce.com/services/Soap/class/AccountInsert';
        public Map<String,String> inputHttpHeaders_x;
        public Map<String,String> outputHttpHeaders_x;
        public String clientCertName_x;
        public String clientCert_x;
        public String clientCertPasswd_x;
        public Integer timeout_x;
        public soapSforceComSchemasClassAccountins.SessionHeader_element SessionHeader;
        public soapSforceComSchemasClassAccountins.DebuggingInfo_element DebuggingInfo;
        public soapSforceComSchemasClassAccountins.CallOptions_element CallOptions;
        public soapSforceComSchemasClassAccountins.DebuggingHeader_element DebuggingHeader;
        public soapSforceComSchemasClassAccountins.AllowFieldTruncationHeader_element AllowFieldTruncationHeader;
        private String SessionHeader_hns = 'SessionHeader=http://soap.sforce.com/schemas/class/AccountInsert';
        private String DebuggingInfo_hns = 'DebuggingInfo=http://soap.sforce.com/schemas/class/AccountInsert';
        private String CallOptions_hns = 'CallOptions=http://soap.sforce.com/schemas/class/AccountInsert';
        private String DebuggingHeader_hns = 'DebuggingHeader=http://soap.sforce.com/schemas/class/AccountInsert';
        private String AllowFieldTruncationHeader_hns = 'AllowFieldTruncationHeader=http://soap.sforce.com/schemas/class/AccountInsert';
        private String[] ns_map_type_info = new String[]{'http://soap.sforce.com/schemas/class/AccountInsert', 'soapSforceComSchemasClassAccountins'};
        public void opportunityUpdate(String Name,String AccountNumber,String Description) {
            soapSforceComSchemasClassAccountins.opportunityUpdate_element request_x = new soapSforceComSchemasClassAccountins.opportunityUpdate_element();
            request_x.Name = Name;
            request_x.AccountNumber = AccountNumber;
            request_x.Description = Description;
            soapSforceComSchemasClassAccountins.opportunityUpdateResponse_element response_x;
            Map<String, soapSforceComSchemasClassAccountins.opportunityUpdateResponse_element> response_map_x = new Map<String, soapSforceComSchemasClassAccountins.opportunityUpdateResponse_element>();
            response_map_x.put('response_x', response_x);
            WebServiceCallout.invoke(
              this,
              request_x,
              response_map_x,
              new String[]{endpoint_x,
              '',
              'http://soap.sforce.com/schemas/class/AccountInsert',
              'opportunityUpdate',
              'http://soap.sforce.com/schemas/class/AccountInsert',
              'opportunityUpdateResponse',
              'soapSforceComSchemasClassAccountins.opportunityUpdateResponse_element'}
            );
            response_x = response_map_x.get('response_x');
        }
}

}
executing through Developer Console from other Salesforce Org:::

soapSforceComSchemasClassAccountins.AccountInsert a = new soapSforceComSchemasClassAccountins.AccountInsert();
a.opportunityUpdate('Microsoft','21232','Cognizant');

Line: 111, Column: 1
System.CalloutException: Web service callout failed: WebService returned a SOAP Fault: 

INVALID_SESSION_ID: Invalid Session ID found in SessionHeader: Illegal Session faultcode=sf:INVALID_SESSION_ID faultactor=